| Abstract: | Three new amidyl radical precursors were developed; PTOC imidate esters, N-acyl PTOC carbamates, and N-phenylthioamides. Amidyl radical generation from PTOC imidate esters and from N-acyl PTOC carbamates utilized the photo-lability of the N-hydroxypyridine-2-thione group to initiate the radical chain reactions. Reaction of N-phenylthioamides with tributyltin hydride resulted in the radical chain reactions of amidyl radicals which are generated by cleavage of the weak N-S bond by thiophilic stannyl radicals. The scope and utility of these radical precursors as means of generating amidyl radicals and conducting subsequent addition reactions with alkenes was examined. Efficient 5-exo cyclization with alkenes on the N-acyl and N-alkyl side chains were demonstrated. Some relative rate constants for reactions of amidyl radicals were determined from competition studies. In reactions of the PTOC derivatives employing additional radical trapping agents, trapping of the carbon centered radicals which resulted from cyclization of amidyl radicals was possible to synthesize a variety of substituted pyrrolidinones and pyrrolidine amides. Through the use of these new and facile methods for radical generation, reactions utilizing amidyl radicals may be useful for the synthesis of nitrogen heterocycles. |
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