Applications of allylamines for the syntheses of aza-heterocycles

Construction of N-Heterocyclic Systems Containing a Fully Substituted Allylic Carbon by Palladium/Phosphine Catalysis

The unique cyclization of benzamide derivatives that contain an alkyne by a Pd(0)/dialkyl(biaryl)phosphine catalytic system is reported. The reaction efficiently provides a variety of six-membered N-heterocyclic compounds that contain a fully substituted carbon center without the need for a stoichiometric additive. Mechanistic studies suggest that this unprecedented cyclization starts with the cleavage of a propargylic C-O bond, and a 1,3-diene has been identified as a relevant intermediate.

A Simple, Broad-Scope Nickel(0) Precatalyst System for the Direct Amination of Allyl Alcohols

The preparation of allylic amines is traditionally accomplished by reactions of amines with reactive electrophiles, such as allylic halides, sulfonates, or oxyphosphonium species; such methods involve hazardous reagents, generate stoichiometric waste streams, and often suffer from side reactions (such as overalkylation). We report here the first broad-scope nickel-catalysed direct amination of allyl alcohols: An inexpensive Ni^II /Zn couple enables the allylation of primary, secondary, and electron-deficient amines without the need for glove-box techniques. Under mild conditions, primary and secondary aliphatic amines react smoothly with a range of allyl alcohols, giving secondary and tertiary amines efficiently. This "totally catalytic" method can also be applied to electron-deficient nitrogen nucleophiles; the practicality of the process was demonstrated in an efficient, gram-scale preparation of the calcium antagonist drug substance flunarizine (Sibelium®).

Design of Two Alternative Routes for the Synthesis of Naftifine and Analogues as Potential Antifungal Agents

Two practical and efficient approaches have been implemented as alternative procedures for the synthesis of naftifine and novel diversely substituted analogues 16 and 20 in good to excellent yields, mediated by Mannich-type reactions as the key step of the processes. In these approaches, the γ-aminoalcohols 15 and 19 were obtained as the key intermediates and their subsequent dehydration catalyzed either by Brønsted acids like H₂SO₄ and HCl or Lewis acid like AlCl₃, respectively, led to naftifine, along with the target allylamines 16 and 20. The antifungal assay results showed that intermediates 18 (bearing both a β-aminoketo- and N-methyl functionalities in their structures) and products 20 were the most active. Particularly, structures 18b, 18c, and the allylamine 20c showed the lowest MIC values, in the 0.5-7.8 µg/mL range, against the dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes. Interesting enough, compound 18b bearing a 4-Br as the substituent of the phenyl ring, also displayed high activity against Candida albicans and Cryptococcus neoformans with MIC₈₀ = 7.8 µg/mL, being fungicide rather than fungistatic with a relevant MFC value = 15.6 µg/mL against C. neoformans.

Metal- and Reagent-Free Intramolecular Oxidative Amination of Tri- and Tetrasubstituted Alkenes

A metal- and reagent-free, electrochemical intramolecular oxidative amination reaction of tri- and tetrasubstituted alkenes has been developed. The electrosynthetic method proceeds through radical cyclization to form the key C-N bond, allowing a variety of hindered tri- and tetrasubstituted olefins to participate in the amination reaction. The result is the efficient synthesis of a host of alkene-bearing cyclic carbamates and ureas and lactams.

Coupling of C(sp3)–H bonds with C(sp2)–O electrophiles: mild, general and selective

The general coupling of amine/ether C(sp³)–H bonds with alkenyl/(hetero)aryl C–O electrophiles is reported with high selectivity.

Enantioselective, Stereodivergent Hydroazidation and Hydroamination of Allenes Catalyzed by Acyclic Diaminocarbene (ADC) Gold(I) Complexes

The gold-catalyzed enantioselective hydroazidation and hydroamination reactions of allenes are presented herein. ADC gold(I) catalysts derived from BINAM were critical for achieving high levels of enantioselectivity in both transformations. The sense of enantioinduction is reversed for the two different nucleophiles, allowing access to both enantiomers of the corresponding allylic amines using the same catalyst enantiomer.

Dual Palladium(II)/Tertiary Amine Catalysis for Asymmetric Regioselective Rearrangements of Allylic Carbamates

The streamlined catalytic access to enantiopure allylic amines as valuable precursors towards chiral β- and γ-aminoalcohols as well as α- and β-aminoacids is desirable for industrial purposes. In this article an enantioselective method is described that transforms achiral allylic alcohols and N-tosylisocyanate in a single step into highly enantioenriched N-tosyl protected allylic amines via an allylic carbamate intermediate. The latter is likely to undergo a cyclisation-induced [3,3]-rearrangement catalysed by a planar chiral pentaphenylferrocene palladacycle in cooperation with a tertiary amine base. The otherwise often indispensable activation of palladacycle catalysts by a silver salt is not required in the present case and there is also no need for an inert gas atmosphere. To further improve the synthetic value, the rearrangement was used to form dimethylaminosulfonyl-protected allylic amines, which can be deprotected under non-reductive conditions.

Zinc and cadmium complexes based on bis-(1H-tetrazol-5-ylmethyl/ylethyl)-amine ligands: structures and photoluminescence properties

Nine zinc and cadmium coordination compounds with bis-(1H-tetrazol-5-ylmethyl/ylethyl)-amine were synthesized and structurally characterized, and the fluorescent emission and fluorescence lifetime of complexes 1–9 have been investigated and discussed.

SO3H-functionalized mesoporous silica materials as solid acid catalyst for facile and solvent-free synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11-trione derivatives

SO₃H-functionalized mesoporous silica materials were used to synthesize 2H-indazolo[2,1-b]phthalazine-1,6,11-trione derivatives in a one-pot three-component condensation reaction.

Kinetic resolution of primary allylic amines via palladium-catalyzed asymmetric allylic alkylation of malononitriles

A new strategy has been developed for the catalytic kinetic resolution of primary allylic amines via enantioselective C–N bond cleavage.

Photoredox α-vinylation of α-amino acids and N-aryl amines

A new coupling protocol has been developed that allows the union of vinyl sulfones with photoredox-generated α-amino radicals to provide allylic amines of broad diversity. Direct C–H vinylations of N-aryl tertiary amines, as well as decarboxylative vinylations of N-Boc α-amino acids, proceed in high yield and with excellent olefin geometry control. The utility of this new allyl amine forming reaction has been demonstrated via the syntheses of several natural products and a number of established pharmacophores.

α-Vinylation of amides with arylacetylenes: synthesis of allylamines under metal-free conditions

A novel methodology for the α-vinylation of amides with arylacetylenes under metal-free conditions has been introduced. This methodology provides a new protocol to synthesize allylamines. In each product, the amount of the cis-isomer was more than that of the trans-isomer.

Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines

Low-valency titanium species, generated in situ by using Ti(OiPr)₄/2 c-C₅H₉MgCl reagent, react with imines to give a titanium-imine complex that can couple with terminal alkynes to provide azatitanacyclopentenes with excellent regioselectivity. Stereodefined allylic amines are obtained in good yields after hydrolysis or iodonolysis of the corresponding azatitanacyclopentenes. When ethynylcyclopropane is used as the coupling partner to react with imines in this reaction, the initially generated allylic amine undergoes an unexpected 1,3-amino migration on silica gel during the column chromatography.

Synthesis and Bioevaluation of Thieno[2,3-d]pyrimidinone Derivatives as Potential Tumor Cell Growth Inhibitors

A series of novel cycloalkylthieno[2,3-d]pyrimidinone derivatives have been conveniently synthesizedviathree steps including G-3CR, heterocyclization, and alkylation reactions as a part of our ongoing search for new bioactive molecules. The newly synthesized compounds were evaluated for their potential tumor cell growth inhibitory activity by standard MTT assay. The preliminary results show that compound6bexhibited better inhibitory activities against HepG2, MCF-7, and BCG-823 cell lines compared to the control.

Rhenium-catalyzed regio- and stereoselective addition of imines to terminal alkynes leading to N-alkylideneallylamines

The reaction of terminal alkynes with imines using ReBr(CO)(5) as a catalyst results in the production of N-alkylideneallylamines and not the conventional propargylamines. The substituent on the imine nitrogen is important, and a diphenylmethyl group gave the best result. The catalytic cycle of this regioselective C-C bond forming reaction appears to involve the formation of an alkynyl rhenium species and subsequent nucleophilic attack of the alkynyl β-carbon atom on the imine carbon to give a vinylidene rhenium species.