作者:Diego J. Cardenas、Antonio M. Echavarren、Angel Vegas
DOI:10.1021/om00015a022
日期:1994.3
Reaction of hydrazones with Pd(PPh3)2Cl2 and sodium acetate in acetonitrile at 65-75-degrees-C gives rise to carbon-bound palladium enolates resulting from direct aliphatic palladation. The reaction has been carried out with the NN-dimethylhydrazones of 2-propanone, 3-methyl-2-butanone, 1-phenyl-1-ethanone, 1-phenyl-1-propanone, and 3,4-dihydro-1(2H)-naphthalenone and with the N-aminopiperidine hydrazone of 2-propanone. The structure of the palladacycle derived from the NN-dimethylhydrazone of 1-phenyl-1-ethanone PhC(=NNMe2)CH2Pd(PPh3)Cl, has been determined by X-ray diffraction. This complex crystallizes in the monoclinic space group P2(1)/n, with a = 10.1806(3) angstrom, b = 21.716(2) angstrom, c = 9.6678(3) angstrom, beta = 100.10(1)-degrees, Z = 4, and V = 2654.20 angstrom3. The complex trans-[Pd(PPh3)(L)Cl2] (L = 1-phenyl-1-ethanone N,N-dimethylhydrazone) was isolated as an intermediate in the formation of the corresponding palladacycle. The palladacycles resulting from aliphatic activation are remarkably stable compounds, even in the presence of beta-hydrogens cis to the Pd(II) center. However, alkyl halides undergo halide exchange with these palladacycles under mild conditions.