Equilibrium constants for keto-enol tautomerisation and migration of hydrogen from carbon to nitrogen to form enamine or zwitterion tautomers have been measured for 2-, 3and 4phenacylpyridines (PyCH,COPh) in aqueous solution at 25 "C. Relative tautomeric stabilities fall in the order ketoimine > enamine > enol and (for the 3-isomer) enol > zwitterion. Values of pKT, (-log KT) where KT = [enamin...

In this issue Yvonne Martin provides us with a ‘‘Perspective’’ addressing an important and too often overlooked problem in chemistry, biology, and drug discovery, tautomerism. As she notes, the extent of this issue goes beyond common expectations. The phenomenon shines a bright light on the limitations of our methods of chemical structure representation and data basing. The problem is multifold...

Abstract The energy profiles for ring opening of representative type B mesoionic 2,3-diphenyl-1,2,3,4-tetrazolium-5-olates, -thiolates, -aminides and –methylides alternative recyclisation pathways are investigated using ab initio MP2 calculations. energetics initial found to be comparable all systems, but the tetrazolium-5-olates anomalous in that no reaction pathway is accessible. influence so...

Four new 1,5-benzothiazepines were synthesized by reaction of o-aminothiophenol with curcumin and curcuminoid β-diketones, in methanol acetic acid. The mechanism involves a Michael addition on the CC double bond affording benzothiazepine two pendant groups, an aryl group adjacent to sulfur atom 1-phenylethanone NH seven membered ring. 1D 2D multinuclear NMR (1H, 13C, 15N, 119F) solution 13C 15N...