Reaction of diphenylmethylene with non-conjugated dienes

Abstract

Reactions of the triplet carbene, diphenylmethylene, with the non-conjugated annular dienes, norbornadiene and cyclo-octa-l,5-diene, have been studied in the hope of achieving transannular addition which might give useful synthetic entry into bridged systems. New compounds were obtained but there was no evidence for the presence of any transannular adducts.SKELL 1-3 has suggested that, whereas singlet carbene may add concertedly to an olefin to yield a cyclopropane, triplet carbene cannot add concertedly to an olefin with spin conservation. The singlet reaction would result in retention of the stereochemistry of the original olefin in the product cyclopropane whereas the triplet reaction would result in loss of this stereospecificity.