Cooperative diastereoselectivity of palladium- and platinum-promoted intramolecular [4+2] Diels-Alder cycloaddition reactions of 3,4-dimethyl-1-phenylphosphole

The complexes [(DMPP)(2)M(CH3CN)(2)]X-2 (DMPP = 3,4-dimethyl-1-phenylphosph ole; M = Pd, Pt; X = BF4-, NO3- ClO4-) react with 2 equiv of the dienophile s N,N-dimethylacrylamide (DMAA), 2-vinylpyridine (VyPy), and diphenylvinylp hosphine (DPVP) to form bis-[4+2] Diels-Alder cycloaddition products. The [ M(DMPP)(2)-(DMAA)(2)](2+) and [M(DMPP)(2)(VyPy)(2)](2+) complexes form excl usively as the cis-geometric isomers, whereas for [M(DMPP)(2)(DPVP)(2)](2+) , both cis- and trans-geometric isomers are formed. The two Diels-Alder cyc loadditions occur sequentially, and the absolute configuration of the first reaction influences the absolute configuration of the second. In all cases , racemic mixtures of the (R,R) and (S,S) diastereomers are formed; none of the meso (R,S) diastereomer is observed. New complexes were characterized by elemental analyses, physical properties, infrared spectroscopy, H-1,H-1{ P-31}, C-13{H-1}, and P-31{H-1} NMR spectroscopy, and, in most cases, X-ray crystallography.