Tungsten(0) alkylidene complexes stabilized as pyridinium ylides: new aspects of their synthesis and reactivity
作者:Henri Rudler、Thomas Durand-Réville
DOI:10.1016/s0022-328x(00)00727-0
日期:2001.1
The interaction of dihydropyridines with alkoxycarbene complexes of tungsten has been shown to lead to pyridinium ylid complexes: this transformation has now been applied to the synthesis of a hydroxyl-containing ylid complex by ring-opening of the pentacarbonyl (2-oxacyclopentylidene) tungsten(0) complex and to the synthesis of a series of chiral ylid complexes both from chiral and non-chiral carbene
Formation and Selective Trapping of 2,5-Dihydropyridine and Its Isopropylidene Derivative by Tungsten(0) Alkylidene Complexes. X-ray Structure of the 5-Isopropylidene-2,5-dihydropyridine Adduct
A mixture of 1,2- and 2,5-dihydropyridines and 5-isopropylidene-2,5-dihydropyridine, obtained from 1-(methoxycarbonyl)-1,2-dihydropyridine and methyllithium followed by protonation, reacts with a series of pentacarbonyl tungsten(0) alkoxycarbene complexes to afford, besides the expected pyridinium ylide complexes 7, the 2,5-dihydropyridinium ylide complexes 6 together with the 5-isopropylidene-2,5-dihydropyridinium ylide complexes 5, which could be separated and fully characterized by X-ray analysis.
Dihydropyridine-induced reductions of methyl(ethoxy)carbene complexes of chromium and tungsten: Formation and x-ray crystal structure of the adduct between pyridine and the corresponding ethylidene carbene complexes
The reactions of [(CO)5MC(OEt)Me] (1) (M = W or Cr) with 1,4-dihydropyridines (R')C5H5N(R) (2) (R = H or Me; R' = H or Me) give either the ylides [(CO)5MCH(Me)(R)NC5H5(R')] (R = H, R' = H or Me) (5) or the pyridinium tungstates and chromates [(CO)5MCH(Me)(OEt)]-[(R)NC5H5-(R')]+ (R = Me, R' = H or 4-Me) (7) via hydride transfer to the carbene carbon atom. Sa (R = H, R' = 4-Me) was characterized spectrally and by single crystal X-ray diffraction.