Dearomatizing Anionic Cyclization of Substituted N-Cumyl-N-benzyl- benzamides on Treatment with LDA: Synthesis of Partially Saturated Substituted Isoindolones
摘要:
[GRAPHICS]On treatment with LDA, substituted N-benzylbenzamides (including those bearing electron withdrawing, electron-donating, or conjugating groups) become lithiated and cyclize to give, after aqueous quench, a range of partially saturated isoindolones as single regio- and stereoisomers, In general, the isoindolones resist rearomatization. Reaction of N-cumyl-N-benzylbenzamides leads to cyclized products which may be deprotected to give N-unsubstituted isoindolones.
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。
Enantioselective one-carbon expansion of aromatic rings by simultaneous formation and chromoselective irradiation of a transient coloured enolate
作者:Rakesh K. Saunthwal、James Mortimer、Andrew J. Orr-Ewing、Jonathan Clayden
DOI:10.1039/d1sc06684f
日期:——
N-benzylbenzamides. The cascade of reactions leading to the products entails enantioselective benzylic deprotonation with a chiral lithium amide, dearomatizing cyclization of the resulting configurationally defined organolithium to give an extended amide enolate, and photochemically induced formal [1,7]-sigmatropic rearrangement and 6π-electrocyclic ring-opening – the latter all evidently being stereospecific
2,3-Dihydroisoindolones by cyclisation and rearomatisation of lithiated benzamides
作者:Jonathan Clayden、Christel J. Menet
DOI:10.1016/s0040-4039(03)00545-8
日期:2003.4
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.
Pyrrolidinone-fused Cyclohexenones by Regioselective Dearomatising Anionic Cyclisation of 2-, 3- or 4-Methoxybenzamides
作者:Jonathan Clayden、Kirill Tchabanenko、Samreen A. Yasin、Michael D. Turnbull
DOI:10.1055/s-2001-10772
日期:——
4-MeOC6H4), cyclized with dearomatization to give Me dienylethers, e.g. II, which were hydrolyzed with dil. HCl to give single stereo- and regioisomers of pyrrolidine-fused cyclohexenones, e.g. III. The bicyclic enones are versatile synthetic intermediates which undergo transformations such as stereoselective redn. and conjugate addn., regioselective Baeyer-Villiger oxidn., bromination and hydrogenation