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, (S C )-1 or (Sc)-3, reacted with dimethylacetylene dicarboxylate, DMAD, and diphenylacetylene to produce exclusively the insertion products (S C )-2, (S C )-4, (S C )-5, and (S C )-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 (S C )-2 to form two stereoisomers of (S C )-7 in a 1.55:1 ratio. However, under similar conditions the insertion product (S C )-4 did not react with N-phenylmaleimide. Complexes (S C )-1 and (S C )-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 (S C )-8 reacted with DMAD to give only one stereoisomer of the insertion product (S C )-7, but under similar conditions the cycloaddition product (S C )-9 did not react with DMAD. New complexes were characterized by elemental analyses, physical properties, polarimetry, 1 H, 1 H{ 3 1 P}, 1 3 C{ 1 H}, and 3 1 P{ 1 H} NMR spectroscopy, and in several cases X-ray crystallography.