DAST-promoted Beckmann rearrangement/intramolecular cyclization of acyclic ketoximes: access to 2-oxazolines, benzimidazoles and benzoxazoles
作者:Huiqin Li、Jian Qin、Zonglian Yang、Xiaoxue Guan、Lin Zhang、Peiqiu Liao、Xingqi Li
DOI:10.1039/c5cc02155c
日期:——
The first example of DAST-promoted Beckmann rearrangement/intramolecular cyclization of acyclic ketoximes is described, which affords 2-oxazolines, benzimidazoles and benzoxazoles.
Efficient and divergent synthesis of fully substituted isoxazoles and spiro-fused pyrazolin-5-ones is developed from cyclopropyl oximes based on selection of reaction conditions. Under Appel conditions (PPh3/CBr4), substituted isoxazoles were synthesized from cyclopropyl oximes via a ring-opening and intramolecular cyclization process, whereas by treatment of cyclopropyl oximes with p-toluenesulfonyl chloride in the presence of potassium hydroxide, spiro-fused pyrazolin-5-ones were obtained via tandem ketoxime tosylation and intramolecular cyclization. (C) 2011 Elsevier Ltd. All rights reserved.