The photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reactions of (R)-(+)-limonene and 2,6-dimethyl-1,6-heptadiene.

摘要

he photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction forms 1:1:1 adducts of nucleophiles, olefins and electron-poor aromatics. The usual aromatic and nucleophile, thus far in the exploration, are 1,4-dicyanobenzene and methanol in acetonitrile. The transformation proceeds by photoinduced electron transfer to the excited aromatic from the olefin.;The potential of the photo-NOCAS reaction to be a synthetic tool has driven studies of the scope and limitations to investigate the intermediate cyclizations of nonconjugated dienes. The interesting dynamics of radical cations and the 1,6-endo, endo cyclization of 2,5-dimethyl-1,5-hexadiene as the radical-cation intermediate of the photo-NOCAS reaction led to the present interest in (R)-(+)-limonene and 2,6-dimethyl-1,6-heptadiene. The photo-NOCAS products of (R)-(+)-limonene are four uncyclized regio- and stereoisomers of photo-NOCAS reaction at the endocyclic double bond. The products of 2,6-dimethyl-1,6-heptadiene are an acyclic photo-NOCAS product, two cyclohexanes (cis and trans) and two cycloheptanes (cis and trans). The cycloheptanes are the products of a 1,7-endo, endo radical-cation cyclization. The cyclohexanes are the results of 1,6-endo cyclization of the intermediate