Fullerene C promoted photochemical hydroamination reactions of an electron deficient alkyne with trimethylsilyl group containing tertiary -alkylbenzylamines.

C-promoted photoaddition reactions of both trimethylsilyl- and a variety of alkyl group containing tertiary benzylamines (, -α-trimethylsilyl--alkylbenzylamines) with dimethyl acetylenedicarboxylate (DMAD) were carried out to explore the synthetic utility of trimethylsilyl group containing tertiary amines as a substrate in the photochemical hydroamination reactions with dimethyl acetylenedicarboxylate (DMAD). The results showed that photoreactions of all the trimethylsilyl containing -alkylbenzylamines with DMAD, under an O-purged environment, produced non-silyl containing enamines efficiently through a pathway involving addition of secondary amines to DMAD, the former of which are produced by hydrolytic cleavage of formed iminium ions. Exceptionally, five-membered N-heterocyclic rings, pyrroles, could be produced competitively in photoreaction of bulky alkyl (, -butyl) group substituted benzylamines through a pathway involving 1,3-dipolar cycloaddition of azomethine ylides to DMAD. Furthermore, C-sensitized photochemical reactions of non-silyl containing benzylamines with DMAD under oxygenated conditions took place in a less efficient and non-regioselective manner to produce enamine photoadducts. The observations made in this study show that regioselectivity of C-promoted photochemical reactions of -α-trimethylsilyl--alkylbenzylamines, leading to formation of secondary amines, can be controlled by the presence of the trimethylsilyl group, and that these trimethylsilyl containing tertiary amines can serve as a precursor of secondary amines for hydroamination reactions with a variety of electron deficient acetylenes.