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.
Stereospecific DearomatisingCyclisation of Tertiary α-Amidoorganolithiums
作者:Jonathan Clayden、Faye E. Knowles、Christel J. Menet
DOI:10.1055/s-2003-40993
日期:——
Lithiation of benzamides derived from a chiral and enantiomericallypure α-methylbenzylamine leads to diastereoselective andregioselective dearomatising cyclisations with overall conservationof the stereochemistry of the starting stereogenic centre.
Synthesis of α-methyl kainic acid by stereospecific lithiation–dearomatizing cyclization of a chiral benzamide
作者:Jonathan Clayden、Faye E Knowles、Christel J Menet
DOI:10.1016/s0040-4039(03)00570-7
日期:2003.4
Stereospecific lithiation of N-α-methylbenzyl benzamides gives configurationally stable tertiary benzyllithiums which undergo a stereospecific dearomatizing cyclization with >99% retention of stereochemistry. The products are partially saturated isoindolinones which carry a new fully-substituted stereogenic centre. A ten-step sequence converts one of these products to the α-methyl analogue of kainic
N -α-甲基苄基苯甲酰胺的立体特异性锂化产生了构型稳定的叔苄基锂,其经历了立体特异性脱芳香化环化反应,并保留了> 99%的立体化学。产品是部分饱和的异吲哚啉酮,带有一个新的完全取代的立体异构中心。十步序列将这些产物之一转化为海藻酸的α-甲基类似物。