Introduction of a phosphorus ylide moiety into [η2-(ω-hydroxy)alkenyl]chromium(0) carbene complexes with Ph3PCCO and consecutive Wittig alkenations with 2-alkynals.: Part 12:: the chemistry of metallacyclic alkenylcarbene complexes

Ketenylidenetriphenylphosphorane, Ph3P=C=C=O (2), reacts selectively with the co-hydroxy group of the alkene-carbene complexes (OC)(4)Cr=C(eta(2)-NMeCH2CH=CHCH2OH)R-1 (1) (R-1 = Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)(4)Cr=C[(4,5-eta(2))-NMeCH2CH=CHCH2O(O)C-CH=PPh3]R-1 (3) (R-1=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R-2-CdropC-CHO (R-2=H, SiMe3, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)(4)Cr=C[(4,5-eta(2))-NMeCH2CH=CHCH2O(O)C-CH=CH-CdropC-R-2]R-1 (4-6) (R-1=Me, R-2=H, SiMe3, Ph: (4a-6a); R-1=Ph, R-2=H, SiMe3, Ph: (4b-6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (H-1, C-13, Si-29, P-31 H-1/H-1 COSY, C-13/H-1 HETCOR, P-31/P-31 EXSY). (C) 2004 Elsevier B.V. All rights reserved.