Cyclotrimerization of phenylethynes to fulvene: reactivity of cis-dichloro(1,1 '-bis(diphenylphosphino)ferrocene)palladium(II)

In the presence of triethylamine (NEt3) and ethanol (EtOH), phenylethyne (o r phenylacetylene, PhC=CH) underwent cyclotrimerization: cis-dichloro(1,1'- bis(diphenylphosphino)ferrocene)palladium(II), [PdCl2(dppf)] (1), reacted w ith phenylethyne to give [Pd(dppf)(2,3,5-triphenylfulvene)] (2). Reaction o f 2 with dimethyl acetylenedicarboxylate in dichloromethane gave [Pd(dppf)( CH3O2CC=CCO2CH3)] (3) and a free 2,3,5 -triphenylfulvene. Crystallographic data for 2.H2O: triclinic space group P (1) over bar, a = 10.658(2), b = 10 .896(2), c = 21.080(3) Angstrom, alpha = 85.303(9)degrees beta = 76.556(9)d egrees, gamma = 80.447(10)degrees, Z = 2, R(wR(2)) = 0.0487(0.1083). (C) 20 00 Elsevier Science B.V. All rights reserved.