Triflic Acid-Catalyzed Dehydrative Amination of 2-Arylethanols with Weak N-Nucleophiles in Hexafluoroisopropanol

The catalytic deoxyamination of readily available 2-arylethanols offers an appealing, simple, and straightforward means of accessing β-(hetero)arylethylamines of biological interest. Yet, it currently represents a great challenge to synthetic chemistry. In most cases, the alcohol has to be either pre-activated in situ or converted into a reactive carbonyl intermediate, limiting the substrate scope for some methods. Examples of direct dehydrative amination of 2-arylethanols are thus still scarce. Here, we describe a catalytic protocol based on the synergy of triflic acid and hexafluoroisopropanol, which enables the direct and stereospecific amination of a broad array of 2-arylethanols, and does not require any pre-activation of the alcohol. This approach yields high value-added products incorporating sulfonamide, amide, urea, and aniline functionalities. In addition, this approach was applied to the sulfidation of 2-arylethanols. Mechanistic experiments and DFT computations indicate the formation of phenonium ions as key intermediates in the reaction.

Quinoline as an Intramolecular Hydride Shuttle in the Deoxygenative Coupling Reaction of Alcohol and the Inert Methyl C(sp3)-H Bond

Reported herein is the C(sp3)-C(sp3) bond-forming at an unactivated C(sp3)-H bond via hydride transfer-initiated deoxygenative coupling reactions. Various polycyclic hydroquinolines were provided under metal-free conditions with excellent diastereoselectivity. Mechanistic study revealed that quinoline served as an intramolecular hydride shuttle to achieve the hydride abstraction and release in order. This methodology not only provides a practical strategy for direct deoxygenative coupling for the C(sp3)-C(sp3) bond-forming but also develops a new reaction type involving quinoline-enabled hydride transfer.

Dehydrative Alkylation of Phenols with Alcohols via Formation of Triflate

An efficient synergistic trityl cation ([Ph3C][B(C6F5)4])/triflic anhydride (Tf2O) catalyzed alkylation of phenols with alcohols is reported. Benefiting from the formation of the triflate in situ, cheap and readily available active alcohols can be used as the alkylating reagents, and the reaction proceeds under mild reaction conditions with a broad substrate scope. This protocol enables the synthesis of ortho-selective phenols and 2,4,6-trisubstitued phenols containing three different alkyl groups. tert-Amyl triflate was synthesized, and mechanistic studies support a triflate-mediated alkylation process.

Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Neutral nickel-catalyzed dehydrosulfonylation of unactivated allylic alcohols under mild conditions

Allyl sulfones are important sulfur-containing compounds that have widespread applications in organic synthesis, medicinal chemistry and materials science. Herein, nickel-catalysed dehydrosulfonylation of unactivated allyl alcohols with aryl sulfonyl hydrazides without additional active agents under mild conditions was developed. A variety of functional allyl sulfones could be efficiently synthesized in the presence of air-stable Ni(acac)2 as the catalyst and 1,1'-bis(diphenylphosphino)ferrocene (DPPF) as the ligand.

Uracil-Cu(i) catalyst: allylation of cyclopropanols with Morita-Baylis-Hillman alcohols under water-tolerant conditions

Inspired by the high affinity of copper with DNA and RNA, a uracil-copper catalytic system was developed to promote ring-opening allylation of cyclopropanols with allylic alcohols under water-tolerant conditions. A new C-OH bond-breaking model can well resolve the trade-off between the need for acidic activators for C(allyl)-OH bond cleavage and the demand for strong basic conditions for generating homoenolates. Therefore, Morita-Baylis-Hillman alcohols, rather than their pre-activated versions, could be incorporated directly into dehydrative cross-coupling with cyclopropanols delivering water as the only by-product. A variety of functionalized δ,ε-unsaturated ketones were obtained in good-to-high yield with high E-selectivity.

Sulfination of Unactivated Allylic Alcohols via Sulfinate-Sulfone Rearrangement

A dehydrative cross-coupling of unactivated allylic alcohols with sulfinic acids was achieved under catalyst-free conditions. This reaction proceeded via allyl sulfination and concomitant allyl sulfinate-sulfone rearrangement. Various allylic sulfones could be obtained in good to excellent yields with water as the only byproduct. This study expands the synthetic toolbox for constructing allylic sulfone molecules.

Interrupted Furan-Yne Cyclization: Access to Unsaturated Dicarbonyl Compounds and Their Subsequent Transformation into Functionalized Pyridazines

The key carbenoid intermediate of transition-metal-catalyzed furan-yne cyclization in Hashmi phenol synthesis could be efficiently intercepted with water under the developed reaction conditions in order to provide access to functionalized unsaturated dicarbonyl compounds that might serve as convenient precursors for the straightforward synthesis of annulated pyridazines.

Organophotoredox-Catalyzed Intermolecular Formal Grob Fragmentation of Cyclic Alcohols with Activated Allylic Acetates

We have developed an efficient method that employs organophotoredox-catalyzed relay Grob fragmentation to facilitate the smooth ring-opening allylation of cyclic alcohols in an environmentally friendly manner. This protocol directly incorporates a wide spectrum of cyclic alcohols and activated allylic acetates into the cross-coupling reaction, eliminating the need for metal catalysts. The process yields a variety of distally unsaturated ketones with good to excellent outcomes and stereoselectivity, while acetic acid is the sole byproduct.

Electrosynthetic C-O Bond Activation in Alcohols and Alcohol Derivatives

Alcohols and their derivatives are ubiquitous and versatile motifs in organic synthesis. Deoxygenative transformations of these compounds are often challenging due to the thermodynamic penalty associated with the cleavage of the C-O bond. However, electrochemically driven redox events have been shown to facilitate the C-O bond cleavage in alcohols and their derivatives either through direct electron transfer or through the use of electron transfer mediators and electroactive catalysts. Herein, a comprehensive overview of preparative electrochemically mediated protocols for C-O bond activation and functionalization is detailed, including direct and indirect electrosynthetic methods, as well as photoelectrochemical strategies.

One-Pot and Unsymmetrical Bis-Allylation of Malononitrile with Conjugated Dienes and Allylic Alcohols

A Pd/Ca catalytic system to promote the unsymmetrical bis-allylation of malononitrile was developed by selecting conjugated dienes and allylic alcohols as allylic reagents. This catalytic system suppressed the competitive symmetrical bis-allylation process and guaranteed the desired unsymmetrical bis-allylation with high chemoselectivity. A wide range of conjugated dienes and allylic alcohols were tolerated well in this transformation, and diverse 1,6-dienes were obtained with high efficiency.

Metal-Free, Adjustable, and Recyclable Catalytic Systems for the Construction of C-C Bonds by Activating Propargylic Alcohols

Pyrano[3,2-c]coumarin derivatives and C3-substituted 4-hydroxycoumarins as important skeletal structures of active natural products and pharmaceutically relevant molecules have received increasing attention. However, developing an adjustable system for selectively synthesizing them is still a challenging task. Herein, sulfonic acid-functionalized ionic liquid was successfully used as the catalyst for the alkylation of 4-hydroxycoumarin derivatives with secondary aromatic propargylic alcohols using dimethyl carbonate as the green solvent, giving up to 98% yield. On the other hand, protonated imidazole-based ionic liquid-catalyzed cyclization was also selectively achieved with a nearly quantitative yield. Developed metal-free catalytic systems exhibited well adjustable and recyclable properties, avoiding the contamination of metal and halogen, reducing the neutralization after the reaction, and benefiting the separation between the catalyst and the product. New strategies were applied for performing the gram-scale reaction smoothly. The adjustable systems might occur through two different mechanisms involving propargylic or allenic carbocation and hydrogen bonding effects between the catalysts and the substrates.

Alcohols as Alkylating Agents in the Cation-Induced Formation of Nitrogen Heterocycles

A Ti(Oi-Pr)4 promoted 5- or 6-endo-trig cyclisation to make nitrogen heterocycles is presented. The utilisation of HFIP as a key solvent enables the stereoselective preparation of di- & tri-substituted pyrrolidines and piperidines while forming a new C-C bond at the same time. The process is triggered by a cationic intermediate generated from an allylic or benzylic alcohol and leads to the simultaneous generation of both a C-C and a C-N bond in a single step. Notably, either 2,3-trans- or 2,3-cis-substituted heterocycles can be obtained by using a nucleophilic amine bearing different substituents. Lastly, the stereoselective synthesis of enantiopure products was achieved by using readily available enantiopure acyclic starting materials.

Dehydrative Cross-Coupling for C-N Bond Construction under Transition-Metal-Free Conditions

A transition-metal-free catalytic system was designed to address the dehydrative cross-coupling of unactivated primary/secondary alcohols with amines/amides under environmentally benign conditions. Mg²⁺ and counteranion (PF₆^-) worked synergistically to realize C-OH bond cleavage and concomitant C-N bond formation. A wide range of allylic alcohols and amines/amides were tolerated well in this transformation, which allowed C-N bond construction with high efficiency.

Carbodefluorination of fluoroalkyl ketones via a carbene-initiated rearrangement strategy

The C-F bond cleavage and C-C bond formation (i.e., carbodefluorination) of readily accessible (per)fluoroalkyl groups constitutes an atom-economical and efficient route to partially fluorinated compounds. However, the selective mono-carbodefluorination of trifluoromethyl (CF3) groups remains a challenge, due to the notorious inertness of C-F bond and the risk of over-defluorination arising from C-F bond strength decrease as the defluorination proceeds. Herein, we report a carbene-initiated rearrangement strategy for the carbodefluorination of fluoroalkyl ketones with β,γ-unsaturated alcohols to provide skeletally and functionally diverse α-mono- and α,α-difluoro-γ,δ-unsaturated ketones. The reaction starts with the formation of silver carbenes from fluoroalkyl N-triftosylhydrazones, followed by nucleophilic attack of a β,γ-unsaturated alcohol to form key silver-coordinated oxonium ylide intermediates, which triggers selective C-F bond cleavage by HF elimination and C-C bond formation through Claisen rearrangement of in situ generated difluorovinyl ether. The origin of chemoselectivity and the reaction mechanism are determined by experimental and DFT calculations. Collectively, this strategy by an intramolecular cascade process offers significant advances over existing stepwise strategies in terms of selectivity, efficiency, functional group tolerance, etc.

Ag(I)-Promoted, Diastereoselective Cyclo-isomerization of N-Alkynyl-7-azaindole-2-carbinols. Selective Synthesis of syn-1,2-Diarylpyrrolo[1,2-a]indol-3-ones and (Z)-8-Benzylideneoxazolo[3',4'':1,5]pyrrolo[2,3-b]pyridines

The design and development of an Ag(I)-promoted, highly diastereoselective cycloisomerization strategy for the synthesis of syn-1,2-diarylpyrrolo[1,2-a]indol-3-ones from N-alkynyl-indole-2-carbinols is reported. The H₂¹⁸O control experiment and identification of ¹⁸O-labeled product suggested the involvement of an external water. The 7-azaindole substrates showned a distinct reactivity to give the (Z)-8-benzylideneoxazolo[3',4':1,5]pyrrolo[2,3-b]pyridines. Key features of this strategy are its 100% atom economy, access to important heterocycles, diverse substrate scope, yields up to 95%, operationally simple procedure, and distinct reactivity of indole vs 7-azaindoles.

Dehydroxylative Alkylation of α-Hydroxy Carboxylic Acid Derivatives via a Spin-Center Shift

A strategically distinct dehydroxylative alkylation reaction of α-hydroxy carboxylic acid derivatives with alkenes is developed. The reaction starts with the attack of a 4-dimethylaminopyridine (DMAP)-boryl radical to the carbonyl oxygen atom, followed by a spin-center shift (SCS) to trigger the C-O bond scission. The resulting α-carbonyl radicals couple with a wide range of alkenes to furnish various alkylated products. This strategy allows for the efficient conversion of a wide array of α-hydroxy amides and esters derived from several biomass molecules and natural products to value-added compounds. Experimental and computational studies verified the reaction mechanism.

Synthesis and Antioxidant/Anti-Inflammatory Activity of 3-Arylphthalides

Phthalides are a group of compounds with relevant biological activities in different areas such as cytotoxicity, anti-stroke activity, neuroprotection, and inflammation, among others. In this study we designed and synthesized a series of 3-arylphthalide derivatives in order to identify their antioxidant and anti-inflammatory activities. The synthetic methodology was established in terms of atom and step economy through a dehydrative coupling reaction between 3-hydroxyphthalide and different properly functionalized arene rings. The evaluation of the antioxidant activity was performed by the ABTS assay and for the anti-inflammatory activity the inhibition of LPS-induced nitric oxide (NO) production in microglial cells Bv.2 and macrophage cells RAW 264.7 was measured. The synthesized compound 3-(2,4-dihydroxyphenyl)phthalide (5a) showed better antioxidant activity than the Trolox standard and caused strong inhibition of NO production in LPS-stimulated Bv.2 and RAW 264.7 cells. In addition, compound 5a reduced the expression of the pro-inflammatory cytokines Il1b and Il6 in RAW 264.7 cells. These results, which are the first account of the anti-inflammatory activity of 3-arylphthalides, suggest that compound 5a could be a promising candidate for more advanced anti-inflammatory studies.

Friedel-Crafts Benzylation of Unprotected Anilines with Indole-3- carbinols to Access Trifluoro-methyl(indolyl)phenylmethanes

:

An unprecedented protocol for the efficient and highly chemoselective alkylation of unprotected anilines with deactivated CF3-indole-3-carbinols promoted by In(OTf)3 has been developed. A series of diversified trifluoromethylated (indolyl)phenylmethanes were produced featuring the C-alkylation in moderate to high chemical yields and with high regioselectivities.

1,2,3-Triazole based ligands with phosphine and pyridine functionalities: synthesis, PdII and PtII chemistry and catalytic studies

This manuscript describes the syntheses of pyridine appended triazole-based mono- and bisphosphines, [o-Ph₂P(C₆H₄){1,2,3-N₃C(Py)C(H)}] (2), [o-Br(C₆H₄){1,2,3-N₃C(Py)C(PPh₂)}] (3), [C₆H₅{1,2,3-N₃C(Py)C(PPh₂)}] (4), [Ph₂P(C₆H₄){1,2,3-N₃C(Py)C(PPh₂)}] (5) and [3-Ph₂P-2-{1,2,3-N₃C(Ph)C(PPh₂)}C₅H₃N] (6), their palladium and platinum chemistry and catalytic applications. These ligands upon treatment with [M(COD)Cl₂] (M = Pd or Pt) yielded complexes with different coordination modes, depending on the reaction conditions. Both κ²-P,N and κ²-P,P coordination modes were observed in many of the complexes indicating the ambidentate nature of these ligands. Monophosphine 2 in the presence of a base afforded rare fused-5,6-membered PCN pincer complexes [MCl{o-Ph₂P(C₆H₄){1,2,3-N₃C(Py)C(H)}}-κ³-P,C,N] (7, M = Pd; 8, M = Pt), whereas the reactions of 4 with [M(COD)Cl₂] (M = Pd, Pt) produced κ²-P,N chelate complexes [MCl₂{C₆H₅{1,2,3-N₃C(Py)C(PPh₂)}-κ²-P,N}] (9, M = Pd; 10, M = Pt). Similar reactions of 5 and 6 resulted in κ²-P,P chelate complexes [MCl₂{{3-Ph₂P-2-{1,2,3-N₃C(Ph)C(PPh₂)}C₅H₃N}-κ²-P,P}] (11, M = Pd; 12, M = Pt) and [MCl₂{3-Ph₂P-2-{1,2,3-N₃C(Ph)C(PPh₂)}C₅H₃N}-κ²-P,P}] (13, M = Pd; 14, M = Pt), respectively. The palladium(II) complexes have shown excellent catalytic activity in the α-alkylation reaction of acetophenone derivatives.

DNA-Compatible Diversification of Indole π-Activated Alcohols via a Direct Dehydrative Coupling Strategy

Indole-based diversification is highly desired in the DNA-encoded chemical library construction. Herein, we present a general strategy for on-DNA synthesis of diverse C3-functionalized indole derivatives via indole π-activated alcohol formation followed by direct dehydrative coupling. Highly efficient bond linkages of C-C, C-N, and C-S were achieved to fuse building blocks that are widely commercially available. DNA-encoding compatibility of the method has been further demonstrated to pave an avenue for application in constructing indole-focused three-dimensional libraries.

Consecutive 2-azidoallylation/click cycloaddition of active methylene for synthesis of functionalized hepta-1,6-dienes with a bis-1,2,3-triazole scaffold

A tandem 2-azidoallylation/click cycloaddition reaction to access novel hepta-1,6-diene skelecton can be successfully accomplished with methylene compounds, phenolic substituted vinyl azide and alkynes in one pot.

Direct activation of alcohols via perrhenate ester formation for an intramolecular dehydrative Friedel–Crafts reaction

A general and highly efficient intramolecular dehydrative Friedel–Crafts reactions via Re2O7 mediated hydroxyl group activation is described for the syntheses of tetrahydronaphthalene, tetrahydroquinoline, tetrahydroisoquinoline, chromane, and isochromane derivatives.

Organocatalytic enantioselective SN1-type dehydrative nucleophilic substitution: access to bis(indolyl)methanes bearing quaternary carbon stereocenters

A highly general and straightforward approach to access chiral bis(indolyl)methanes (BIMs) bearing quaternary stereocenters has been realized via enantioconvergent dehydrative nucleophilic substitution. A broad range of 3,3'-, 3,2'- and 3,1'-BIMs were obtained under mild conditions with excellent efficiency and enantioselectivity (80 examples, up to 98% yield and >99 : 1 er). By utilizing racemic 3-indolyl tertiary alcohols as precursors of alkyl electrophiles and indoles as C-H nucleophiles, this organocatalytic strategy avoids pre-activation of substrates and produces water as the only by-product. Mechanistic studies suggest a formal SN1-type pathway enabled by chiral phosphoric acid catalysis. The practicability of the obtained enantioenriched BIMs was further demonstrated by versatile transformation and high antimicrobial activities (3al, MIC: 1 μg mL-1).

Synthesis of 3-halogenated 2,3'-biindoles by a copper-mediated 2,3-difunctionalization of indoles

A copper-mediated 2,3-difunctionalization of indoles to afford 3-halogenated 2,3'-biindoles is described herein. The protocol uses readily available feedstocks and a naturally abundant copper catalyst system, which allows the regioselective formation of C-C and C-X (X = Cl & Br) bonds in one single operation. Here the copper metal salt serves not only as a catalyst but also as a reactant to provide the source of halogen. This operationally simple procedure avoids the utilization of environmentally unfriendly reagents and displays good functional group compatibility. Noteworthily, the introduction of halogen into molecules would offer great potential for further chemical transformations.

Titanium(IV)-Mediated Ring-Opening/Dehydroxylative Cross-Coupling of Diaryl-Substituted Methanols with Cyclopropanol Derivatives

A titanium(IV)-mediated ring-opening/dehydroxylative cross-coupling of diaryl-substituted methanols with a cyclopropanol derivative was developed. The reactions proceeded efficiently to provide synthetically useful γ,γ-diaryl esters in moderate to good yields, which could be applied to the functionalization of complex molecules derived from bioactive fenofibrate and isoxepac and the synthesis of a precursor of Zoloft.

Transition-metal-free and base promoted C-C bond formation via C-N bond cleavage of organoammonium salts

A transition-metal-free and base promoted C-C bond forming reaction of benzyl C(sp³)-H bond with organoammonium salts via C-N bond cleavage has been reported. Benzyl ammonium salts as well as cinnamyl ammonium salt could couple readily with various benzyl C(sp³)-H species, producing the corresponding products in moderate to excellent yields with good functional group tolerance. Late stage chemical manipulation enabled the specific 1,2-diarylethane structure of products transformed into useful olefin compounds via dehydrogenation, which further demonstrated the utility of this reaction.

Direct Cross-Coupling of Alcohols with O-Nucleophiles Mediated by N-Iodosuccinimide as a Precatalyst under Mild Reaction Conditions

We report N-iodosuccinimide as the most efficient and selective precatalyst among the N-halosuccinimides for dehydrative O-alkylation reactions between various alcohols under high-substrate concentration reaction conditions. The protocol is non-metal, one-pot, selective, and easily scalable, with excellent yields; enhancing the green chemical profiles of these transformations.

Fe-Catalysed Coupling Reactions Between Alkynes and Alcohols

In this review, we discussed about the synthetic developments in the field of Fe-catalysis for the formation of - bonds through the coupling of alkynes and alcohols, for the period of 13 years (2008-2020). These strategies fulfil important Green Chemistry principles, as they are highly atom economic (up to 100 %), no toxic by-products (only water), employs highly abundant and low toxic alcohols (no need for any pre-functionalization hence step economy) and cheaper Fe-catalysts. Having these advantages, one can predict that in the coming years a large number of fascinating new iron-catalyzed reactions will be developed for the organic synthesis. We hope that this review article will be highly useful for the synthetic community to design and develop new Fe-catalyzed coupling reactions and keeps the content in the right prospect.

Hemisynthesis and Biological Evaluation of Cinnamylated, Benzylated, and Prenylated Dihydrochalcones from a Common Bio-Sourced Precursor

Several families of naturally occurring C-alkylated dihydrochalcones display a broad range of biological activities, including antimicrobial and cytotoxic properties, depending on their alkylation sidechain. The catalytic Friedel-Crafts alkylation of the readily available aglycon moiety of neohesperidin dihydrochalcone was performed using cinnamyl, benzyl, and isoprenyl alcohols. This procedure provided a straightforward access to a series of derivatives that were structurally related to natural balsacones, uvaretin, and erioschalcones, respectively. The antibacterial and cytotoxic potential of these novel analogs was evaluated in vitro and highlighted some relations between the structure and the pharmacological properties of alkylated dihydrochalcones.

Dehydrative Allylation of Alkenyl sp2 C-H Bonds

We designed a cooperative catalytic system by combining commercially available Ca(NTf₂)PF₆ and Pd(PPh₃)₄ to address the dehydrative allylation of alkenyl sp² C-H bonds in an environmentally benign manner. A novel C-OH bond cleavage method was found to be crucial for this practical protocol. A variety of alkenes and allylic alcohols equipped with wide-spectrum functional groups can be successfully incorporated into the desired cross-coupling, affording 1,4-dienes with moderate to excellent yields and high stereo- and regioselectivity.

Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides

As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp²)-C(sp³) bonds, in which free alcohols and aryl bromides-both readily available chemicals-can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage arylation of several structurally complex natural products and pharmaceuticals.

De Novo and Divergent Synthesis of Highly Functionalized Furans by Cascade Reactions of 2-Hydroxy-1,4-diones with Nucleophiles

Herein, a divergent synthesis of a variety of 2α- and 5α-substituted furan derivatives from 2-hydroxy-1,4-diones is reported. By using appropriate substrates and an acid catalyst, the reactions occurred selectively through cyclization/1,6-conjugate addition or cyclization/Friedel-Crafts-type cascade reactions. A broad range of nucleophilic reagents (>10 types for the 1,6-conjugate addition for 5α substitution and >20 types for the Friedel-Crafts-type cascade reaction for 2α substitution), including alcohols, amides, furan, thiophene, pyrrole, indole, phenols, and many others, can successfully participate in the reactions, providing a universal strategy for a diversity-oriented synthesis of α-substituted furan derivatives. Deuteriation experiments and DFT calculations were carried out to support the proposed reaction mechanisms. Antifungal activity experiments revealed that products with an indole or 4-hydroxycoumarin core substituted at the 2α position showed moderate activities against Rhizoctorzia solani and Botrytis cinerea, respectively.

Divergent Gold Catalysis: Unlocking Molecular Diversity through Catalyst Control

The catalyst-directed divergent synthesis, commonly termed as "divergent catalysis", has emerged as a promising technique as it allows chartering of structurally distinct products from common substrates simply by modulating the catalyst system. In this regard, gold complexes emerged as powerful catalysts as they offer unique reactivity profiles as compared to various other transition metal catalysts, primarily due to their salient electronic and geometrical features. Owing to the tunable soft π-acidic nature, gold catalysts not only evolved as superior contenders for catalyzing the reactions of alkynes, alkenes, and allenes but also, more intriguingly, have been found to provide divergent reaction pathways over other π-acid catalysts such as Ag, Pt, Pd, Rh, Cu, In, Sc, Hg, Zn, etc. The recent past has witnessed a renaissance in such examples wherein, by choosing gold catalysts over other transition metal catalysts or by fine-tuning the ligands, counteranions or oxidation states of the gold catalyst itself, a complete reactivity switch was observed. However, reviews documenting such examples are sporadic; as a result, most of the reports of this kind remained scattered in the literature, thereby hampering further development of this burgeoning field. By conceptualizing the idea of "Divergent Gold Catalysis (DGC)", this review aims to consolidate all such reports and provide a unified approach necessary to pave the way for further advancement of this exciting area. Based on the factors governing the divergence in product formation, an explicit classification of DGC has been provided. To gain a fundamental understanding of the divergence in observed reactivities and selectivities, the review is accompanied by mechanistic insights at appropriate places.

An efficient approach for the synthesis of novel methyl sulfones in acetic acid medium and evaluation of antimicrobial activity

A series of nine methyl sulphones ( 3a –3 i ) starting from the aldehydes ( 1a–1i ) were synthesized in two consecutive steps. In the first step, preparation of allyl alcohols ( 2a–2i ) from their corresponding aldehydes by the reaction of sodium borohydride in methanol at room temperature is reported. Finally, methyl sulphones are synthesized by condensing sodium methyl sulfinates with allyl alcohols in the presence of BF ₃ .Et ₂ O in acetic acid medium at room temperature for about 2–3 h. The reaction conditions are simple, yields are high (85%–95%), and the products were obtained with good purity. All the synthesized compounds were characterized by their ¹ H, ¹³ C NMR, and mass spectral analysis. All the title compounds were screened for antimicrobial activity. Among the compounds tested, the compound 3f has inhibited both Gram positive and Gram negative bacteria effectively and compound 3i has shown potent antifungal activity. These promising components may help to develop more potent drugs in the near future for the treatment of bacterial and fungal infections.

Practical allylation with unactivated allylic alcohols under mild conditions

A practical palladium/calcium catalytic system was developed for dehydrative allylation with unactivated allylic alcohols.