Conversion of thioamides and N 2-acyl-N 1-methyl-N 1-thioacylhydrazines into amides and N 1 N 2-diacyl-N 1-methylhydrazines by trimethyloxonium fluoroborate
Titanium enolates and “ate” complexes of N,N-disubstituted amides and thioamides in the Michael reaction.
作者:Lilia Z. Viteva、Tzveta S. Gospodova、Yuri N. Stefanovsky
DOI:10.1016/s0040-4020(01)85243-1
日期:1994.1
The synthetic potential, regio- and stereoselectivity of titanium dialkylamide and dialkylthioamide enolates and “ate” complexes in reaction with some conjugate carbonyl compounds are investigated. Titaniumenolates react preferentially in 1,2-position while “ate” complexes afford 1,4-regiocontrol. The stereochemical behaviour of the latter follows in general the lithium and potassium precursors. Marked
AbstractN,N‐diisopropylamides and ‐thioamides show hindered rotation around the NCH bonds, and the presence of mixtures of conformational isomers can be demonstrated at temperatures below 273 K in solution. 1H and 13C NMR spectra of these conformers are measured and assigned. The 13C data serve to study through‐space effects on 13C chemical shifts, which strongly depend on the conformations of the isopropyl groups. For amides, a through‐space shielding of the N‐methine carbons is found to exist only for conformers in which the methine hydrogen atom is spatially close to the oxygen atom. Chemical shift differences between amides and thioamides can be rationalized in terms of through‐bond and through‐space contributions, and serve for a better understanding of the shift differences in N,N‐dialkylamides and ‐thioamides.
MUKHERJEE R., INDIAN J. CHEM. <IJOC-AP>, 1977, B 15, NO 6, 502-505