X=Y-ZH compounds as potential 1,3-dipoles. Part 64: Synthesis of highly substituted conformationally restricted and spiro nitropyrrolidines via Ag(I) catalysed azomethine ylide cycloadditions

13-Dipolar reactions of imines of both acyclic and cyclic alpha-amino esters with a range of nitroolefins using a combination of AgOAc or Ag(2)O with NEt(3) are described. In most cases the reactions were highly regio and stereospecific and endo-cycloadducts were obtained in good yield. However, in a few cases the initially formed cycloadducts underwent base catalysed epimerisation. The stereochemistry of the cycloadducts was assigned from NOE data and established unequivocally in several cases by X-ray crystallography. (C) 2008 Elsevier Ltd. All Fights reserved.