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

The chiral cyclopalladated complexes containing coordinated 3,4-dimethyl-1-phenylphosphole, DMPP, and an N-donor ligand, (S_c)-l or (S_c)-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_cc)-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)-l 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, ¹H, ¹H{³¹P}, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy, and in several cases X-ray crystallography.