2,3-Dihydroisoindolones by cyclisation and rearomatisation of lithiated benzamides
摘要:
Lithiation of tertiary aromatic N-benzyl amides generates [alpha]-amido benzyllithiums which cyclise with dearomatisation to cyclic extended enolates. Rearomatisation by oxidation, or, in the case of methoxy-substituted enolates, elimination, yields 2,3-dihydroisoindoles. Enantiomerically enriched products may be formed either by using a chiral base to lithiate the starting material or by using a chiral starting material. (C) 2003 Elsevier Science Ltd. All rights reserved.
Stereospecific Photochemical Ring Expansion of Lithiated Benzamides
作者:Jonathan Clayden、Faye E. Knowles、Christel J. Menet
DOI:10.1021/ja035827i
日期:2003.8.1
provides, according to the substitution pattern of the starting amides, either norcaradienes or cycloheptadienones by overall insertion of the N-benzyl group into the benzamide's aromatic ring system. Chiral benzamides undergo the ringexpansion with high (sometimes complete) stereospecificity. The reaction appears to occur via a series of pericyclic reactions (photochemical or thermal sigmatropic rearrangements
用强碱(LDA 或 t-BuLi)处理 N-苄基苯甲酰胺,然后用 500 W 钨灯照射,根据起始酰胺的取代模式,通过 N-苄基的整体插入,提供降卡二烯或环庚二烯酮基团进入苯甲酰胺的芳环系统。手性苯甲酰胺以高(有时是完全的)立体特异性进行环扩展。该反应似乎是通过一系列周环反应(光化学或热 sigmatropic 重排和热电环反应)在初始脱芳构化环化后发生的。