Palladium-catalyzed addition of alkynes to cyclopropenes

Abstract

The palladium catalyzed coupling of alkynes and cyclopropenes provides a powerful method for the synthesis of alkynylcyclopropanes, proceeding under mild conditions in the presence of many functional groups (such as esters, carboxylic acids, aldehydes, and alcohols).

Addition Reactions: Polar Addition

“…86 Palladium-catalysed addition of terminal alkynes to cyclopropenes affords alkynylcyclopropanes under mild conditions; a number of functional groups (esters, carboxylic acids, aldehydes, and alcohols) are tolerated. 87 A highly efficient and regioselective methoxycarbonylation of terminal alkyl-and aryl-alkenes (RCH=CH 2 ) can be attained via a palladium-salicylic borate-catalysed protocol. The substrates include aliphatic alkenes, allylbenzenes, and styrene derivatives.…”

“…tetrasubstituted thiophene derivatives (87). Here, the amine played the dual role of a base and a nucleophile.…”

Enantioselective Hydroalkynylation of Non‐Polar Carbon‐Carbon Double Bonds: Iridium‐Catalyzed Asymmetric Addition Reaction of Terminal Alkyne CH Bonds to Substituted Norbornadienes

“…Thes uccessfule nantioselective hydroalkynylationo ft his type of system has sporadically been reported.W eh erein describe our progress for the example of vinyl-substituted norbornadiene derivatives.W ith the aid of an iridium complex in combination with the chiral SYN-PHOS ligand, the addition products couldb eo btained smoothlyw ith excellent enantioselectivities (up to 99% ee). In particular, the first examples of an acetylenic C À Hb onda dding across azanorbornadienes are also disclosed.Keywords: alkynes; asymmetric catalysis; C À H bonds;iridium; synthetic methods Hydroalkynylations of polarc arbon-oxygen/nitrogen doubleb onds,f or instance,o fa ldehydes,k etones, imines,e nones and related compounds,h ave been remarkably successfuls ince the late 1980s.[1] In fact, it is not surprising that this addition reactiono ffers exceptionallyh igh regioselectivity across the polarized carbon center.[2] Even thoughe xtensivep rogress in carbonyl-type hydroalkynylations hasb een achieved, the regioselective and enantioselective addition of the terminal alkyne C À Hb ondt oanon-polar or nonfunctionalized C=Cd ouble bond is stillagreat challenge.[3] Recently,chemists have employed specially ligated transitionm etal complexes to promote reactions between terminal alkynesa nd allenes, [4] 1,3-dienes, [5] cyclopropenes, [6] norbornadienes, [7] andvinylarenes.[8] Yet, only non-enantioselectivev ersionso f these reactions were mainly reported. Thed evelopment of asymmetric hydroalkynylations of non-polar C=Cb onds remains limited.…”

Alkynylcyclopropanes from Terminal Alkynes through Consecutive Coupling to Fischer Carbene Complexes and Selective Propargylene Transfer

“…[5] In fact, such a system is generally made by alkynylation of appropriate cyclopropane precursors. [6] It would be of interest to design synthetic equivalents of propargyl carbenes for regioselective cyclopropanation (Scheme 1). In this context, the intramolecular cyclopropanation of w-alkenylpropargyl alcohols in the presence of Bi-A C H T U N G T R E N N U N G (OTf) 3 (OTf = triflate) has been successfully addressed by Komeyama et al [7] In relation to the intermolecular process, a sole particular case has been described with 2-(alk-1-yn-1yl)-2-(trialkylsilyl)-1,3-dithianes and [Cp 2 Ti{PA C H T U N G T R E N N U N G (OEt) 3 } 2 ], in which the cyclopropanation is directed by the trialkylsilyl group.…”

“…Firstly, bisA C H T U N G T R E N N U N G (alkynyl)carbenes 3 react with methylenecyclopentane or cyclopentadiene providing butadiynylcyclopropanes in a regioselective manner. The Bu/Ph-substituted carbene 3 reacted with methylenecyclopentene at the C b ÀBu carbon atom to yield a single regioisomer (6), whereas the reaction between cyclopentadiene and the PCP/TIPS-substituted carbene 3 provided 7 through the reaction at the C b À PCP carbon atom. Compound 7 was slightly contaminated (< 5 %) with the isomer resulting from the reaction of the C b À TIPS carbon atom and cyclopentadiene.…”