Et<sub>2</sub>Zn-Mediated Rearrangement of Bromohydrins
作者:Lezhen Li、Peijie Cai、Qingxiang Guo、Song Xue
DOI:10.1021/jo800231s
日期:2008.5.1
and highly efficient method for the rearrangement of bromohydrins mediated by Et2Zn to synthesize carbonylcompounds was described. Various β-bromo alcohols were treated with 0.6 equiv of Et2Zn to form a zinc complex in CH2Cl2 at room temperature for 2 h, followed by 1,2-migration to give the corresponding carbonylcompounds. This remarkable and clean rearrangement is general for acyclic and cyclic bromohydrins
One Step Preparation of 1,4-Diketones from Methyl Ketones and α-Bromomethyl Ketones in the Presence of ZnCl2 · t-BuOH · Et2NR as a Condensation Agent
作者:Natali M. Nevar、Alexander V. Kel'in †、Oleg G. Kulinkovich
DOI:10.1055/s-2000-6418
日期:——
1,4-Diketones have been prepared in one step from methyl ketones and α-bromomethyl ketones under the action of ZnCl2 · t-BuOH · Et2NR as a condensation agent with moderate to high yields. The mechanistic pathway of the reaction is proposed to go through aldol condensation of ketones followed by 1,3-dehydrobromination of aldol products and cleavage of activated cyclopropyl intermediates.
NMR studies of tin enolates 1, in the presence of HMPA, revealed the presence of a five-coordinate O-stannyl enolate 1(h) which contributes to upfield shifts of Sn peaks in the Sn-119 NMR spectrum and increased coupling constants J(Sn-119-C-13), compared with the four-coordinate tin enolate 1(e). The tautomeric equilibrium between C-stannyl ketone 1(k) and O-stannyl enolate 1(e) was changed by the addition of HMPA, the percentage of enol form being increased. The resulting five-coordinate tin enolates 1(h) showed high reactivity and selectivity for halide displacement in reactions with alpha-halo ketones 2. The tin enolates, when coordinated by Bu(4)NBr, effected a selective reaction with alpha-halo imines 5 to give a variety of gamma-imino ketones 6, which were subsequently hydrolyzed to 1,4-diketones or cyclodehydrated to substituted pyrroles 9.
Kulinkovich, O. G.; Kel'in, A. V.; Senin, P. V., Russian Journal of Organic Chemistry, 1995, vol. 31, # 8, p. 1060 - 1062
作者:Kulinkovich, O. G.、Kel'in, A. V.、Senin, P. V.
DOI:——
日期:——
Kel'in, A. V.; Kulinkovich, O. G., Russian Journal of Organic Chemistry, 1994, vol. 30, # 2.1, p. 202 - 206