Synthetic and Theoretical Aspects of New Dimroth Rearrangement of6-Aminopyran-2-ones to 6-Hydroxypyridin-2-ones via Carbamoyl Ketenes
作者:Julia O. Subbotina、Walter M. F. Fabian、Evgeniy V. Tarasov、Natalia N. Volkova、Vasiliy A. Bakulev
DOI:10.1002/ejoc.200400875
日期:2005.7
ide 4b, were observed. The first one represents a new, Dimroth-type rearrangement and proceeds by thermal opening of the pyrane ring, followed by the simultaneous rotational isomerization of the ketene intermediate 7 (s-cis) to 7 (s-trans) and its recyclization onto the amido group to form the pyridin-2-one cycle.The first step of the rearrangement has a calculated [B3LYP/6-31G(d)] activation barrier
6-氨基-4-氧代吡喃并[3,4-d] [1,2,3]噻二唑1的两种热转化方向,导致6-羟基-4-氧代-[1,2,3]噻二唑观察到[4,5-c]吡啶2或2-氰基-2-(1,2,3-噻二唑-5-基)乙酰胺4b。第一个代表新的 Dimroth 型重排,并通过吡喃环的热开环进行,然后同时将烯酮中间体 7(s-cis)旋转异构化为 7(s-trans)并将其再环化到酰胺基上基团形成 pyridin-2-one 循环。重排的第一步计算出的 [B3LYP/6-31G(d)] 激活势垒为 24–34 kcal/mol,胺的参与将其降低了约 5 kcal/mol [PCM-B3LYP/6-31G(d), DMSO]。相反,计算到酰胺基上的再循环步骤基本上是无障碍的(ΔE < 2 kcal/mol)。还研究了取代基,特别是那些能够形成分子内氢键的取代基对优选反应路径的影响。经计算,吡喃循环的替代开环至少比 Dimroth