Expanding the scope of the Newman-Kwart rearrangement - A computational assessment

The Newman-Kwart rearrangement (NKR) has been Studied for a variety of thioncarbamates using density functional (B3LYP) and ab initio (MP2) methodologies. The results confirm and support the generally accepted mechanism that the NKR proceeds through a four-membered cyclic transition state. The presence of a pi system connected via an oxygen linkage to a thiocarbonyl functionality is identified as a crucial structural element for the NKR. The calculations further suggest that the NKR might also be feasible for thioncarbamates derived front pi system containing groups other than phenols Such as ethenol, ethenediol, and butadienol. The NKR is compared with the Schonberg rear-rangements of thioncarbonates.