Reactivity Studies of the 4,5-Didehydroquinolinium and 4,5-Didehydroisoquinolinium Biradicals Toward Amino Acids and Dipeptides

摘要

Biradicals 5 and 6 give reaction products similar to those of monoradicals, but additional products are also observed due to the presence and close proximity of the two radical sites. The large EA and small S-T gap of these radicals rationalize the observation of greater reactivity than observed for monoradicals. Biradical 7 showed drastically different reactivity toward the amino acids and dipeptides. For example, H abstraction is the the major reaction for amino acids while individual amino acids react mainly by adduct formation. The larger number of H atoms present in the dipeptides may make H abstraction kinetically favored over adduct formation. Also, as the size of the substrate increases, steric hindrance may interfere with adduct formation.