Ring-opening reactions of methylenecyclopropanes promoted by metal halides

A New Method of Constructing Methyleneindene and Quinoline Frameworks from Methylenecyclopropanes

In this paper, we have established an operationally convenient protocol for the rapid construction of polysubstituted methyleneindene and quinoline derivatives under mild conditions. This new synthetic method is achieved through the conversion of acetyl-substituted methylenecyclopropanes with TsOH ⋅ H2O and ortho-amino-substituted methylenecyclopropanes with aromatic aldehyde and TsOH ⋅ H2O, respectively. A variety of transformations of the obtained products was demonstrated. The plausible reaction mechanisms were also proposed.

Visible-light-induced reactions of methylenecyclopropanes (MCPs)

Diverse, visible-light-induced transformations of methylenecyclopropanes (MCPs) have been reported in recent years, attracting significant attention from synthetic chemists. As readily accessible strained molecules, MCPs have sufficient reactivity to selectively generate different target products, through reactions with various radical species upon visible-light irradiation under regulated reaction conditions. These transformations can be classified into three subcategories of reaction pathway, forming ring-opened products, cyclopropane derivatives, and alkynes. These products include pharmaceutical intermediates and polycyclic/heterocyclic compounds that are challenging to obtain using traditional methods. This review summarizes the recent advancements in this field.

Copper catalyzed borocarbonylation of benzylidenecyclopropanes through selective proximal C-C bond cleavage: synthesis of γ-boryl-γ,δ-unsaturated carbonyl compounds

A copper catalyzed borocarbonylation of BCPs via proximal C-C bond cleavage for the synthesis of γ-boryl-γ,δ-unsaturated carbonyl compounds has been developed. Using substituted benzylidenecyclopropanes (BCPs) and chloroformates as starting material, a broad range of γ-boryl-γ,δ-unsaturated esters were prepared in moderate to excellent yields with excellent regio- and stereoselectivity. Besides, when aliphatic acid chlorides were used in this reaction, γ-boryl-γ,δ-unsaturated ketones could be produced in excellent yields. When substituted BCPs were used as substrates, the borocarbonylation occurred predominantly at the proximal C-C bond trans to the phenyl group in a regio- and stereoselective manner, which leads to the Z-isomers as the products. This efficient methodology involves the cleavage of a C-C bond and the formation of a C-C bond as well as a C-B bond, and provides a new method for the proximal C-C bond difunctionalization of BCPs.

Construction of an isoquinolinone framework from carboxylic-ester-directed umpolung ring opening of methylenecyclopropanes

An interesting type of reaction involving functionalized methylenecyclopropanes (MCPs) has been revealed. Here, a nucleophilic attack of an anionic species onto a partially polarity-reversed MCP was realized by treating a neighbouring carboxylic ester tethered to the MCP and amine with KHMDS to realize an umpolung ring opening of the MCP. This work established an operationally convenient protocol for the rapid construction of isoquinolinone frameworks.

A facile method for the synthesis of dihydroquinoline-azide from the Lewis acid-catalyzed reaction of alkylidenecyclopropanes with TMSN3

A facile method for the cascade azidation of alkylidenecyclopropanes catalyzed by In(OTf)₃is developed, affording azido compounds in moderate to good yields.

A facile method for the synthesis of trifluoromethylthio-/chloro-homoallylic alcohols from methylenecyclopropanes

Trifluoromethylthiolated/chloro-homoallylic alcohols have been directly accessed by the reaction of (PhSO₂)₂NSCF₃/Cl with methylenecyclopropanes (MCPs) in DMF in moderate to good yields.

Iron-catalyzed or iodine-induced intramolecular halocyclization of N-vinyl-tethered methylenecyclopropanes: facile access to halogenated 1,2-dihydroquinolines

Iron(iii) catalyst or I₂ acts as a Lewis acid to activate enamines, affording the corresponding halogenated 1,2-dihydroquinolines in good yields.

A method for synthesis of homoallylic bromide

Cyclopropyl Grignard reagents react with carbonyl compounds in the presence of diethyl phosphite to give homoallylic bromides. The reaction is effectively carried out under mild conditions in a one-pot fashion with moderate to good yields.

Applications of bismuth(III) compounds in organic synthesis

This review article summarizes the applications of bismuth(III) compounds in organic synthesis since 2002. Although there are an increasing number of reports on applications of bismuth(III) salts in polymerization reactions, and their importance is acknowledged, they are not included in this review. This review is largely organized by the reaction type although some reactions can clearly be placed in multiple sections. While every effort has been made to include all relevant reports in this field, any omission is inadvertent and we apologize in advance for the same (358 references).

Synthesis of the indene, THF, and pyrrolidine skeletons by Lewis acid mediated cycloaddition of methylenecyclopropanes with aldehydes, N-tosyl aldimines, and acetals

Methylenecyclopropanes (MCPs 1) react with aldehydes, N-tosyl aldimines, and acetals to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF3 x OEt2 under mild reaction conditions. Some special transformations of MCPs 1 with aldehydes have been reported in this paper. A plausible reaction mechanism has been discussed, which is based on a deuterium-labeling experiment and the Prins-type reaction mechanism.

Silica Gel Triggered Transformations of 3-Methylenecyclopropylmethyl Sulfonates to 3-Methylenecyclobutyl Analogues: Experimental and Computational Studies

Methylenecyclopropylcarbinols treated with sulfonyl chloride and Et(3)N form the sulfonated products in almost quantitative yields, which can be transformed to the corresponding 3-methylenecyclobutyl sulfonates with silica gel chromatography work-up. The rational explanation was proposed on the basis of computational studies.

Lewis acid catalyzed ring-opening reactions of methylenecyclopropanes with diphenylphosphine oxide in the presence of sulfur or selenium

Methylenecyclopropanes undergo an interesting Lewis acid-catalyzed ring-opening reaction with diphenylphosphine oxide in the presence of sulfur or selenium upon heating at 85 degrees C in 1,2-dichloroethane to give the corresponding homoallylic thiol or selenol derivatives in good to high yields.

Lewis Acid-Catalyzed Rearrangement of Multi-Substituted Arylvinylidenecyclopropanes

An interesting rearrangement of arylvinylidenecyclopropanes having three substituents at the 1- and 2-positions of the corresponding cyclopropane catalyzed by Lewis acids to give 6aH-benzo[c]fluorine derivatives via a double intramolecular Friedel-Crafts reaction or to give an indene derivative via an intramolecular Friedel-Crafts reaction is described.

Palladium-Catalyzed Isomerization of Methylenecyclopropanes in Acetic Acid

[reaction: see text] Pd(PPh3)4-catalyzed isomerization of MCPs 1 in acetic acid proceeds smoothly at 80 degrees C in toluene to give the corresponding 1-substituted or 1,1-disubstituted dienes 2 in good to excellent yields under mild conditions. The plausible mechanism has been disclosed on the basis of a deuterium-labeling experiment.

Facile synthesis of multisubstituted buta-1,3-dienes via Suzuki-Miyaura and Kumada cross-coupling strategy of 2,4-diiodo-buta-1-enes with arylboronic acids and Grignard reagents

One-pot Suzuki-Miyaura-type and Kumada-type cross-coupling reactions of 2,4-diiodo-buta-1-enes with arylboronic acids and alkyl/aryl magnesium bromides were carried out in the presence of accessibly simple catalysts under mild conditions. As a result, some 1,1,2-trisubstituted buta-1,3-dienes were obtained including the Tamoxifen-type, which have potential adjuvant therapy in women who have suffered from breast cancer and cyclooxygenase-2-type (COX-2-type) inhibitors, some of which have been proved to elicit efficient anti-inflammatory analgesic activities and less adverse gastrointestinal side effects and to be very useful in the prophylactic treatment of a wide variety of cancers and neurodegenerative disorders.

Lewis acid mediated endo-cyclisation of trimethylsilylmethylenecyclopropyl imines—a stereoselective route to indolizidines

Lewis acid mediated endo-cyclisation of trimethylsilylmethylenecyclopropyl imines provides a stereoselective route to indolizidines via a novel cascade sequence.

Lewis acid-mediated cycloaddition of methylenecyclopropanes with aldehydes and imines: a facile access to indene, THF, and pyrrolidine skeletons via homoallylic rearrangement protocol

Methylenecyclopropanes (MCPs) 1 can react with aldehydes and aldimines to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF(3).OEt(2) under mild reaction conditions.