Organometallic reactions of α-haloimines as a useful tool in organic synthesis
作者:Norbert de Kimpe、Bart de Corte、Roland Verhe、Laurent de Buyck、Niceas Schamp
DOI:10.1016/s0040-4039(01)80111-8
日期:1984.1
The reaction of organometallic reagents, e.g. alkyllithiums, cuprates and alkylcoppers, with α-haloimines gave selectively a variety of synthetically usefulreactions, including coupling to 1,4-diimines, homologation, and production of heterocycles.
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.