Of nitrogen radicals in pyrrolidine synthesis

In common with the general increasing interest in synthetic applications of free-radical cyclizations, this year has seen a high level of interest in the synthesis of nitrogen heterocycles by such processes. Padwa et al. have reported the synthesis of a range of N-benzenesulphonyl-pyrrolidines (220) and -piperidines... 

Azides are highly valuable radical acceptors that form nitrogen-centered radicals after addition onto them, as in the case of the transformation of 31 into 32. This reaction opens new possibilities for making pyrrolidines. Murphy, for instance, disclosed the synthesis of ( )-horsfihne and ( )-coerulescine by tandem cyclization of iodoaryl alkenyl azides such as 29 [42]. By the same strategy and using precursor 33, formal syntheses of ( )-vindohne [43] and ( )-aspidospermidine [44] have been rendered possible (Scheme 10). 

The synthesis of nicotine has shown that the group substituted in the j3-position is pyrrolidine ring (559) in which the hydrogen atom joined to the nitrogen atom has been replaced by a methyl radical —... 

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