NMR Studies of Five-Coordinate Tin Enolate: An Efficient Reagent for Halo Selective Reaction toward .alpha.-Halo Ketone or .alpha.-Halo Imine
摘要:
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.
Synthesis of 2-imino-4-thiazolines, 2-imino-4-alkoxythiazolidines, thiazoles and 4-imidazolin-2-ones from α-halomethyl ketimines
作者:Norbert De Kimpe、Wim De Cock、Marian Keppens、Dirk De Smaele、Andrea Mészáros
DOI:10.1002/jhet.5570330429
日期:1996.7
nes, 3,4-disubstituted-4-methoxy-2-iminothiazolidines, 2,4-disubstituted-thiazoles, 2-amino-4-substituted-thiazoles and 1,5-disubstituted-4-imidazolin-2-ones, were synthesized from α-chloromethyl and α-bromomethyl ketimines by condensation with potassium thiocyanate, thiourea, ammonium thiocyanate and potassium cyanate.
The highly coordinated tin hydride, Bu(2)SnClH-HMPA (B), is shown to be an effective agent for the reduction of imines. The subsequent alkylation of the resulting intermediate tin amides permitted the preparation of a series of tertiary amines in a one-pot procedure. The spectral identification of the novel tin hydrides, B and Bu(2)SnClH-Bu(4)NF, was accomplished by H-1, C-13, and Sn-119 NMR and FT-IR studies.