Captodative substituent effects in radical chemistry (ref. 1)

Abstract

Polar substituents are generally more efficient for the stabilisation of ions than for radicals. These last species are more and more recognised as important intermediates in chemistry and in biochemistry. The cumulative effect of two substituents of the same polarity shows antagonism for radical stabilisation whereas captodative (cd) substituents show synergy. Synthetic applications of the cd-effect use the breaking of adjacent weak “proradical” C-H and C-C bonds. Further, cd-double bonds are useful as radical traps and as partners in cycloaddition reactions. cd-N-vinyl substitution induces with complete stereocontrol the epoxy-epimination rearrangement of chiral oxazines and opens a new route to inosite and streptamine derivatives. © 1988 IUPAC