Transition-Metal Catalyzed Addition/Cyclization Of 1,6-Diynes With Silaboronate Reagent

Transition-metal catalyzed addition/cyclization of non-conjugated 1,6-diynes has been demonstrated as a fascinating method to construct the highly substituted 1,2-dialkylidenecycloalkanes.This strategy offers an efficient tool for the preparation of medicinal molecules and natural products.In this work,we mainly introduced the palladium-catalyzed silaborative/carbocyclization of 1,6-diynes and the proto-silylation/carbocyclization of 1,6-diynes catalyzed by copper catalyst to obtain the functional 1,2-dialkylidenecyclopentane products.1,6-Diynes reacted with PhMe2Si-B(pin)in the presence of palladium catalyst to afford the 1,2-dialkylidenecycloalkanes bearing silyl and boryl groups with a(Z,Z)-configuration in good to excellent yields.Moreover,the corresponding products could be easily converted into other synthetically useful compounds.Significantly,the compounds can be selectively converted into the terminally boryl-substituted 1,3-dienes in good yields via protodesilylation.So far,there is no strategy available to access this kind of boryl-substituted 1,2-dialkylidenecyclopentane compounds via direct hydroboration of unconjugated diynes.Moreover,this boryl-substituted 1,3-diene compound is also a convenient reagent for Suzuki cross-coupling reaction.This silaborative/carbocyclization reaction allows a catalytic amount of palladium as the catalyst,tetrahydrofuran as the solvent,at a mild temperature,to constructe(Z,Z)-1,2-dialkylenecyclopentanes with good to excellent regio-and stereoselectivities,as well as a wide substrate scope.We would like to develop a cheaper metal catalyzed addition/cyclization reaction.Therefore,a proto-silylation/cyclization reaction of 1,6-diynes with the(dimethylphenylsilyl)pinacolborane catalyzed by copper catalyst for the synthesis of(Z)-configuration 1,2-dialkylenecycloalkanes was developed.The corresponding products can react with various dienophiles via Diels-Alder reacton to construct spiro-cyclic products.In addition,with the utility of chiral oxazoline ligands and copper catalyst,the asymmetric proto-silylation/cyclization of 1,6-diyne compounds was investigated.The proto-silylation/cyclization reaction has the following advantages:1)relatively cheaper metal copper as the catalyst;2)selective(Z)-configuration products would be formed;3)simple and mild condition,tolerance to a wide range of functional groups.