1501-90-2Relevant academic research and scientific papers
New reactions of the thiocarbonyl function. The synthesis of hindered peptides
Barton, Derek H. R.,Ferreira, J. Albert
, p. 1 - 20 (1997)
The well-known radical chemistry of the thiocarbonyl function has been expanded to include the concerted reaction between an O-acyl derivative of N-hydroxypyridine-2(1H)-thione (a Barton PTOC ester) and a sulfenamide. The atom-economical process spawned a carboxamide and an unsymmetrical disulfide of synthetic and biological value. The reaction was successfully applied to the synthesis of sterically encumbered, urethane-protected dipeptides. The oxidation-reduction technology pertaining to the disulfide-phosphine combination facilitated the generation of transient Barton PTOC esters. In conjunction with the appropriate benzenesulfenamide, the Barton PTOC ester of benzoyl-L-leucine was shown to preserve optical integrity according to the sensitive Young test, albeit at low temperature. However, the thermodynamic forces at play are powerful and, as a result, the yields were not compromised. In all but the sterically demanding instances, the parent free amine almost matched the reaction time, yield, and enantiomeric excess of the corresponding benzenesulfenamide in its reaction with a Barton PTOC ester.
N-hydroxypyridine-2(1H)-thione derivatives of carboxylic acids as activated esters. Part I. The synthesis of carboxamides
Barton, Derek H. R.,Ferreira, J. Albert
, p. 9347 - 9366 (2007/10/03)
The reaction between an acyl derivative of N-hydroxypyridine-2(1H)- thione (a Barton PTOC ester) and either an amine (primary or secondary), or the corresponding sulfenamide, led to the formation of a carboxamide in a clean transformation requiring minimal work-up and purification. The reaction with a sulfenamide is particularly useful since the only by-product, an unsymmetrical disulfide, is of both synthetic and biological value. In sterically demanding cases, Barton PTOC esters were more reactive towards benzenesulfenamides than to the corresponding free amines.
