Reaction-Environment-Dependent Photoaddition Reactions of -Phenyl Amino Acid Esters Possessing a Silyl Group with Fullerene C: Selective Formation of Aminomethyl-1,2-dihydrofullerenes vs Fulleropyrrolidines.

The current study investigates SET-promoted photoaddition reactions of the silyl-group-containing -phenylglycinates and -phenylalaninates, -((trimethylsilyl)methyl)--phenyl-substituted glycinates and alaninates, respectively, with fullerene C to explore how the types of amino acid esters (AAEs) and molecular oxygen affect the photoaddition reaction efficiencies and chemoselectivity of in situ formed radical cations of AAEs. The results showed that under deoxygenated (N-purged) conditions, photoreactions of -phenylglycinates with C produced aminomethyl-1,2-dihydrofullerenes through the addition of α-amino radicals arising by sequential SET and desilylation processes from initially formed secondary anilines to C. In oxygenated conditions, photoreactions of -phenylglycinates with C, albeit less efficient, took place to form fulleropyrrolidines through a pathway involving 1,3-dipolar cycloaddition of azomethine ylides to C assisted by in situ formed O. The same types of photoproducts were observed with -phenylalaninates, though the reactions were less efficient. The use of methylene blue (MB) as a photosensitizer in the photoreactions under oxygenated conditions was especially effective in enhancing the efficiency of fulleropyrrolidine formation. These results demonstrate that photoaddition reactions of silyl-tether-containing -phenyl AAEs with C can be governed by the reaction conditions and the presence or absence of a photosensitizer employed.