STUDY OF CIS TRANS AND ENDO/EXO DIASTEREOSELECTIVITY 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 functio n attached at C-2 of furans in the yield and diastereoselectivity of [ 4+3] cycloaddition reactions with oxyallyl cations is presented. In al most all studied furans a cis diastereospecificity and a high endo dia stereoseleciivity is observed. Increasing bulkyness of the function at tached at C-2 of furans, increases the endo diastereoselectivity, but decreases yield. Increasing the electronic density of the furan system , by an electron donating group attached at C-2, increases yield and d iastereoselectivity.