Base-induced cycloreversion of nitrile oxide cycloadducts: conversion of imines into secondary and tertiary amides and aromatic aldehydes into acids without a conventional oxidising agent
作者:R. Alan Aitken、Swati V. Raut
DOI:10.1039/p19960000747
日期:——
protonated to give secondary amides or treated in situ with alkyl halides to give tertiaryamides in moderate to good overall yield, although the reaction is restricted to examples with an aromatic substituent at the 5-position. The 1,4,2-dioxazoles 15, formed by cycloaddition of benzonitrile oxide to aromaticaldehydes, similarly undergo cycloreversion allowing direct conversion either into substituted
Dearomatising cyclisations of lithiated N-benzylbenzamides
作者:Anjum Ahmed、Jonathan Clayden、Samreen A. Yasin
DOI:10.1039/a808218i
日期:——
On treatment with ButLi in the presence of HMPA, N-benzylbenzamides undergo anionic cyclisation with dearomatisation to give an extended amide enolate which reacts with electrophiles to yield bicyclic cyclohexadiene derivatives.
The chemoselective cleavage of C–N bonds of amides, sulfonamides, and acylsulfonamides by aluminum halides is described. AlCl3 and AlI3 display complementary reactivities toward N-alkyl and N-acyl moieties. N-Alkylacylsulfonamides, secondary N-(tert-butyl)sulfonamides, and tertiary N-(tert-butyl)amides undergo N-dealkylation upon treatments with AlI3 generated in situ from aluminum and iodine in acetonitrile
The invention relates to a method for producing amides or esters from carboxylic acids and from an amine constituent or alcohol constituent in the presence of a 1,3,5-triazine and optionally in the presence of an organic solvent and of a tertiary amine. According to the invention, a (bi)cyclic diamine or an adduct formed therefrom with the triazine constituent is used as a tertiary amine in a preferred stoichiometric ratio of diamine to the triazine constituent ranging from 0.30 to 1.10; the stoichiometric ratio of carboxylic acid to the amine constituent or alcohol constituent should range from 0.2 to 5.0, and; the molar ratio of carboxylic acid to the triazine constituent ranges from 0.5 to 1.5. Amino acids such as N-protected amino acids and peptides serve as carboxylic acid constituents and (C-protected) amino acids or a C-protected peptide serve as the amine constituent. 2-chlorine-4,6-dimethoxy-1,3,5-triazine (CDMT) is used as the preferred 1,3,5-triazine, and the N,N′-dimethyl-1,4-piperazine is used as the cyclic diamine. In addition to this method, which can be carried out at temperatures ranging from −80 to +150 ° C. and in the presence of an organic solvent, the invention also relates to adducts comprised of (bi)cyclic diamine and 1,3,5-triazine. Compared to the prior art, higher yields with shorter reaction times are achieved using the described method, and distinctly smaller waste quantities of tertiary amine bases accrue.
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。