Selective Formation of Spiro Dihydrofurans and Cyclopropanes Through Unexpected Reaction of Aldehydes with 1,3-Dicarbonyl Compounds

Deoxygenative Cyclopropanation of Aldehydes with Acyl-Stabilized Sulfur Ylides

Herein, we described a novel [1+1+1] deoxygenative cyclopropanation between sulfur ylides and aldehydes, which is distinctive from traditional epoxidation reactions. The method offers a straightforward approach for the synthesis of highly stereoselective, functionalized, and structurally diverse tertiary cyclopropyl thioethers. The reaction demonstrates a broad substrate scope and excellent compatibility with various functional groups, rendering it particularly suitable for the late-stage modifications of pharmaceuticals and natural products, as well as the synthesis of structurally diverse compounds. Additionally, β,β-disubstituted enals can also engage in the deoxygenative cyclopropanation reaction, instead of undergoing classic cyclopropanation through a Michael addition reaction-induced cyclization with sulfur ylides, thus yielding synthetically important vinylcyclopropanes with excellent chemoselectivity and diastereoselectivity.

Copper acetate catalysed C-C bond formation en route to the synthesis of spiro indanedione cyclopropylpyrazolones

This article reports the synthesis of spiro compounds based on an indanedione-cyclopropane-pyrazolone framework. The reaction relied upon the Michael-initiated ring closure strategy and was carried out under Cu(OAc)₂ catalysis, assisted by an oxygen atmosphere and the base Et₃N. The final compounds were obtained as an inseparable mixture in most cases with modest to good yields using diverse substrates. Among the two plausible routes, computational studies indicated the feasibility of a route which involves a four-membered Cu containing intermediate. Given the generic nature of the developed method, it may be utilised to synthesise other analogous spiro systems.

One-Pot Synthesis of Benzoazole-Substituted Thioenamines via a Cross Dehydrogenation Coupling (CDC) Reaction

An iodine-catalyzed synthesis of benzoazole-substituted thioenamines in a one-pot manner was reported. Using 2-aminothiophenols (or 2-aminophenols or 1,2-phenylenediamines), tetramethylthiuram disulfide (TMTD), and enamines (mainly indoles) as starting materials, the target C(sp²)-S formation products (benzoazole-substituted thioenamines) could be furnished smoothly in good yields. The reaction might proceed through an electrophilic substitution pathway in a cross dehydrogenation coupling (CDC) manner. The protocol is metal-free and features easy performance, a one-pot manner, a good functional group tolerance, and good yields.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Green pseudo-multicomponent synthesis of some new spirocyclopropane derivatives via electro-catalyzed reaction

Due to the diverse applications of cyclopropane analogs in bioorganic, medicinal, and pharmaceutical chemistry, a clean and efficient procedure was established to synthesize spirocyclopropane via an electrochemical reaction which involves a sequence of Michael addition, halogenation, and intramolecular ring-closing reaction. In this study, an environmentally benign synthesis of spirocyclopropane was carried out through the condensation of indan-1,3-dione by aromatic aldehydes or 2-benzylidenemalononitrile derivatives. Constant current electrosynthesis was applied to a mixture of propanol containing sodium bromide as an electrolyte and a brominating agent at room temperature, respectively.

Chemoselective syntheses of spirodihydrofuryl and spirocyclopropyl barbiturates via cascade reactions of barbiturate-based olefins and acetylacetone

The Michael addition initiated ring closure reaction of barbiturate-based olefins and acetylacetone with NBS has been explored. The efficient and chemoselective approach for the synthesis of barbiturate-fused spirocycles was established. Spirodihydrofuryl barbiturates and spirocyclopropyl barbiturates were synthesized selectively via cascade reactions under different basic conditions in moderate to excellent yields. The structure of 2-(4-chlorophenyl)-1,1-diacetyl-5,7-dimethyl-5,7-diazaspiro[2,5]octane-4,6,8-trione was confirmed by single crystal X-ray diffraction analysis.

Merging catalyst-free synthesis and iodine catalysis: one-pot synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones

A new and efficient one-pot strategy combining catalyst-free synthesis and iodine catalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones. This approach affords products in moderate to high yields (up to 96%) with excellent diastereoselectivities (up to >25 : 1 dr). The reaction is simple to carry out and is metal-free.

A new and efficient one-pot strategy combining catalyst-free synthesis and iodine catalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones.

One-Pot Multicomponent Mechanosynthesis of Polysubstituted trans-2,3-Dihydropyrroles and Pyrroles from Amines, Alkyne Esters, and Chalcones

An efficient and practical one-pot multicomponent reaction of amines with alkyne esters and chalcones promoted by I₂/PhI(OAc)₂ has been developed under solvent-free ball-milling conditions to afford a variety of polysubstituted trans-2,3-dihydropyrroles in moderate to good yields. The present method features a short reaction time, mild reaction conditions, broad substrate scope, and feasibility of large-scale synthesis. Intriguingly, this protocol can also furnish the corresponding synthetically more attractive pyrroles with the addition of an oxidant in a one-pot way.

One-pot asymmetric synthesis of a spiro[dihydrofurocoumarin/pyrazolone] scaffold by a Michael addition/I2-mediated cyclization sequence

An asymmetric formal one-pot reaction of 4-hydroxycoumarins with unsaturated pyrazolones has been developed by merging a chiral bifunctional organocatalyst with molecular iodine, which furnished a series of optically active spiro[dihydrofurocoumarin/pyrazolone] heterocycles with spiro quaternary stereogenic centers in moderate to excellent yields (up to 99%) with excellent diastereoselectivities (up to >99 : 1 dr) and good to excellent enantioselectivities (up to 99% ee). The application in the gram-scale synthesis of chiral spiro[dihydrofurocoumarin/pyrazolone] compounds was also successfully realized.

Diastereoselective Synthesis of Spirocyclopropanes under Mild Conditions via Formal [2 + 1] Cycloadditions Using 2,3-Dioxo-4-benzylidene-pyrrolidines

A highly diastereoselective cyclopropanation of cyclic enones with sulfur ylides was developed under catalyst-free conditions, producing multifunctional spirocyclopropanes in generally excellent yields (up to 99% yield and >99:1 d.r.). The asymmetric version of this method was realized by using an easily available chiral sulfur ylide, affording products with moderate to good stereoselectivity.

The molecular diversity scope of 1,3-indandione in organic synthesis

Indandione is an important starting material that has drawn great attention in various organic transformations because of its attributes, such as low cost, easy to handle and eco-friendliness generally affording the corresponding products in excellent yields. In this review, we summarize recent data describing the most important MCRs reactions in which one of the starting materials is indandione. This review will also present two-, three-, four-, and five-component and one-pot reactions for the functionalization of indandione with the to increase awareness on the versatility of using this compound among organic chemists.

[Cp*RhCl2]2: mechanosynthesis and applications in C–H bond functionalisations under ball-milling conditions

Under LAG conditions, [Cp*RhCl₂]₂ was prepared by mechanochemical synthesis and applied in directed C–H bond funtionalisations.

Synthesis of an extended halogen-bonded metal–organic structure in a one-pot mechanochemical reaction that combines covalent bonding, coordination chemistry and supramolecular synthesis

We describe a four-component one-pot mechanochemical reaction which combines the formation of covalent bonds, coordination bonds and halogen bonds to obtain an extended structure based on halogen-bonded metal–organic units.