Study of cis/transand endo/exoDiastereoselectivity in the [4+3]-Cycloaddition Reaction of 2-Functionalized Furans and Dimethyloxyallyl Cation: Preparation of Versatile Cycloheptane Synthons

A study on the influence of steric and electronic effects of a function attached at C-2 of furans in the yield and diastereoselectivity of [4+3] cycloaddition reactions with oxyallyl cations is presented. In almost all studied furans a cisdiastereospecificity and a high endodiastereoselectivity is observed. Increasing bulkyness of the function attached at C-2 of furans, increases the endodiastereoselectivity, but decreases yield. Increasing the electronic density of the furan system, by an electron donating group attached at C-2, increases yield and diastereoselectivity.