Use of a radical clock to study the photodecarboxylation of amino acidatocobalt(III) complexes

The products of steady state UV irradiation of amino acidatobis(2,2'-bipyri dine)cobalt(III) complexes have been identified. The products of these phot odecarboxylation reactions include a carbonyl compound derived from the ami no acid side chain. The viability of an aminocyclopropylmethyl radical cloc k as a potential mechanistic probe for the reaction was assessed by ab init io methods. The required cyclopropylglycine containing substrate was synthe sized and used to show that reaction of an alpha-carbon centred radical mus t be a fast step if it occurs in the reaction sequence leading to formation of the intermediate metallacyclic complexes.