Metal complexes of biologically important ligands, CXXI. Orthopalladated enolates from N-(diphenylmethylene) Schiff bases of alpha-amino acid esters as ambivalent 1,3-dipoles in [2+3] cycloadditions. Structures of a series of cycloadducts

Enolates of ortho-palladated N-(diphenylmethylene) Schiff bases from glycin e esters (R3P)Pd[(C6H4)(C6H5)C=N-C(R')=CO2R] were isolated and have been sh own to be ambivalent 1,3-dipoles in [2+3] cycloadditions. Tetracyanoethene, dimethyl acetylene dicarboxylate, dimethyl azodicarboxylate, thiobenzophen one, thione-S, 4-phenyl-1,2,4-triazoline-3,5-dione, diphenyl-ketene and phe nylisocyanate are added at the palladium and the enolate (alpha-C) carbon a toms, whereas methyl propiolate, methyl acrylate, and the methyl esters of maleic and fumaric acid form [2+3] cycloadducts with the alpha-carbon and t he imino carbon atoms of the enolates under mild conditions. The structures of seven cycloadducts were determined by X-ray diffraction analyses.