Dynamic Diastereoselectivity during Iron Carbonyl Mediated Spirocyclization Reactions
摘要:
Dynamic diastereoselectivity during Fe(CO)(3) promoted [6 + 2] ene spirocyclization of 35a and 35b, having a chiral center on the pendent side chain, was investigated and gave rise to products 28a and 28b instead of four possible isomers. From this reaction, two chiral centers are generated, with absolute stereochemistry determined by the double bond geometry and the chiral center already present. 28a/b and the diene product from demetallation of 28a are proposed as potential intermediates for total synthesis of 18-deoxycytochalasin H. Furthermore, a stepwise second cyclization and a tandem double cyclization mediated by the Fe(CO)(3) moiety was investigated.
Darstellung von Dreikernclustern durch Umwandlung von Fe3(CO)112- und Fe4(CO)132-
作者:W. Deck、A.K. Powell、H. Vahrenkamp
DOI:10.1016/0022-328x(91)83048-9
日期:1991.7
[PNN]2[Fe3(CO)11] and [PNN]2[Fe4(CO)13] with organotransition metal halides are described. In all cases a fragmentation of the Fe cluster framework occurs. A common side product resulting from hydride abstraction is [PNN][HFe3(CO)11], the structure of which was determined. Both starting cluster yield [PNN][MFe2(CO)12] (M = Mn, Re) with (CO)5MnBr and (CO)5ReBr, respectively. The structure of [PNN][MnFe2(CO)12]
eliminate R3ESnR′3 (E = C, Si, Sn) from iron complexes containing two main-group IV ligands on reaction with phosphines are only successful for methyl stannyl complexes. mer(CO)3(Ph3P)Fe(SnMe3)SiMePh2 eliminates the siloxy stannane Ph2MeSiOSnMe3 instead. The complexes mer-(CO)3(Ph3P)Fe(SnMe3)[Si(OEt)3] and mer-(CO)3(Ph3P)Fe(SnMe3)2 decompose under SnMe4 elimination to form [(CO)3(Ph3P)Fe(μ-SnMe2)]n
作者:Michael I. Bruce、George A. Koutsantonis、Edward R.T. Tiekink
DOI:10.1016/0022-328x(91)86317-j
日期:1991.4
Reactions between Ir(C2Ph)(CO)2(PPh3)2 and iron carbonyls (Fe(CO)5, Fe2(CO)9 have given FeIr clusters Fe2Ir(μ3-C2Ph)(CO)9−n(PPh3)n (n = 1 (8), 2) and FeIr2(μ3-PhC2C2Ph)(CO)7(PPh3)2 (9). The Rh analogue of 8 was obtained similarly. Substitution of IrPPh3 by PEt3, and addition of PEt3 to Cα of the acetylide ligand in 8 gave zwitterionic Fe2Ir(μ3-PhC2PEt3)(CO)8(PEt3) (12), which on heating was converted
Effect of fluorine and trifluoromethyl substitution on the donor properties and stereodynamical behaviour of triarylphosphines
作者:James A. S. Howell、Natalie Fey、Jonathan D. Lovatt、Paul C. Yates、Patrick McArdle、Desmond Cunningham、Einat Sadeh、Hugo E. Gottlieb、Zeev Goldschmidt、Michael B. Hursthouse、Mark E. Light
DOI:10.1039/a903211h
日期:——
A series of 2-, 3- or 4-trifluoromethyl substituted triarylphosphines and their oxide, chalcogenide and Fe(CO)4 derivatives have been prepared and characterised spectroscopically and crystallographically. Electronic effects of CF3 substitution are cumulative and felt equally in the 2, 3 or 4 position. Substitution in the 2 position substantially hinders the complexing ability for steric reasons. Correlated P–C rotation in the 2-substituted derivatives has been analysed by variable temperature NMR and molecular mechanics calculations.
Preparation and reactions of triphenylphosphine and triphenyl phosphite complexes of (benzylideneacetone)dicarbonyliron(0)
作者:Brian F. G. Johnson、Jack Lewis、G. Richard Stephenson、Eduardo J. S. Vichi
DOI:10.1039/dt9780000369
日期:——
(Benzylideneacetone)dicarbonyl(triphenylphosphine)iron(0), [Fe(bda)(CO)2(PPh3)], has been prepared by irradiating [Fe(CO)4(PPh3)], in benzene, in the presence of benzylideneacetone (bda). The related triphenyl phosphite complex has been prepared thermally. These complexes are found to be useful precursors for the preparation of complexes of the type [Fe(diene)(CO)2L](L = a phosphine or phosphite ligand)