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

摘要

The chiral cyclopalladated complexes containing coordinated 3,4-dimethyl-1-phenylphosphole, DMPP, and an N-donor ligand, (S-C)-1 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 under-went [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, H-1, H-1{P-31}, C-13{H-1}, and P-31{H-1} NMR spectroscopy, and in several cases X-ray crystallography. [References: 62]