53545-13-4Relevant academic research and scientific papers
Thioenols and thioamides substituted by two β-EWGs. Comparison with analogous amides and enols
Basheer, Ahmad,Rappoport, Zvi
, p. 483 - 491 (2008)
Condensation of organic isothiocyanates with active methylene compounds gave nine thioamides RNHCSCHYY' or their isomeric thioenols RNHC(SH) = CYY' for substrates in which Y and Y' are electron-withdrawing groups (EWG). These included derivatives of Meldrum's acid (MA) which showed 100% thioenol in all solvents. For other compounds the percentages of thioenol in CDCI3 when R = Ph are 100% when Y = CN and Y'= CO2Me or Y' = CO 2CH2CCI3, 6% when Y = Y'= CO2CH 2CF3, and 0% when Y = Y' = CO2Me. The chemical shift of SH (highest values 12.0-16.0 ppm) served as a probe for the thioenol structures and also for the extent of hydrogen bonding to the SH group. In contrast to simple ketones and thioketones in which thioenolization is favored over enolization by factors as large as 106, for intramolecular competition KThioenol/KEnol ratios are much lower than for systems not substituted by β-EWGs. X-ray crystallography of the 5-anilido-MA derivative shows a hydrogen-bonded thioenol structure. δ(OH), δ(NH), KEnol, and crystallographic data for analogous thioenol and enol systems are compared. Copyright
