Comparative study of the reactions of two alkynes and an alkene with chiral cyclopalladated complexes derived from N , N -dimethyl-α-(2-naphthyl)ethylamine and N , N -dimethyl-α-methylbenzylamine: Insertion or cycloaddition.

Abstract

The chiral cyclopalladated complexes containing coordinated 3,4-dimethyl-1-phenylphosphole, DMPP, and an N-donor ligand, (Sc)-l or (Sc)-3, reacted with dimethylacetylene dicarboxylate, DMAD, and diphenylacetylene to produce exclusively the insertion products (Sc)-2, (Sc)-4, (Sc)-5, and (Sc)-6, respectively, although [4+2] Diels - Alder cycloaddition reactions between DMAD or diphenylacetylene and coordinated DMPP were possible. N-Phenylmaleimide underwent [4+2] Diels - Alder cycloaddition to the coordinated DMPP in the insertion product (Sc)-2 to form two stereoisomers of (Scc)-7 in a 1.55:1 ratio. However, under similar conditions the insertion product (Sc)-4 did not react with N-phenylmaleimide. Complexes (Sc)-l and (Sc)-3 reacted with N-phenylmaleimide to give only one enantiomer of the [4+2] Diels - Alder cycloaddition product, although two diastereomeric products were possible in each reaction. The cycloaddition product (Sc)-8 reacted with DMAD to give only one stereoisomer of the insertion product (Sc)-7, but under similar conditions the cycloaddition product (Sc)-9 did not react with DMAD. New complexes were characterized by elemental analyses, physical properties, polarimetry, 1H, 1H{31P}, 13C{1H}, and 31P{1H} NMR spectroscopy, and in several cases X-ray crystallography.