据报道,一种易于获得的有机-无机杂化催化剂用于α-卤代羰基化合物的还原断裂。稳健的杂化催化剂是 ZnCl 2 Lewis 酸和吖啶橙作为光活性有机染料的自稳定组合。已经使用光物理和电化学实验详细研究了这种混合催化剂的机械特性。一项系统的研究使我们能够发现合适的路易斯酸以有效地稳定α-卤代羰基化合物,从而降低标准有机染料范围内的还原电位。该策略通过引导光氧化还原循环通过氧化猝灭途径解决了脱卤氢化或烷基自由基同源偶联等问题。光活性有机染料和路易斯酸对应物之间的协同作用通过有效和受控地生成烷基自由基,使功能化与广泛的偶联伙伴成为可能,并作为昂贵的后过渡金属基光催化剂的合适替代品。为了证明这种协同催化体系的应用潜力,研究了四种不同的α-羰基溴的合成转化,具有广泛的底物范围。
for the synthesis of various sulfur-tethered vinylogous carbonates in good to excellent yields. Important features of the developed reaction include wide functional group tolerance, excellent chemo- and regioselectivity, and efficient rearrangement involving the carbonyl motif. The present reaction also equally works well with α-selenoesters for the synthesis of seleno-containing vinylogous carbonates
General synthesis of alkyl phenyl selenides from organic halides mediated by zinc in aqueous medium
作者:Lothar W Bieber、Ana C.P.F de Sá、Paulo H Menezes、Simone M.C Gonçalves
DOI:10.1016/s0040-4039(01)00820-6
日期:2001.7
halides of different structural types react with diphenyl diselenide and zinc dust in aqueous medium to give alkyl phenyl selenides. Benzylic and allylic bromides, α-bromoesters, acids and ketones and some primary alkyl iodides produce high yields even under acidic conditions. Less reactive halides need basic medium. The reaction proceeds equally well in the presence of various unprotected functional
不同结构类型的有机卤化物与二苯基二硒化物和锌粉在水性介质中反应,生成烷基苯基硒化物。苄基和烯丙基溴化物,α-溴代酸酯,酸和酮以及某些伯烷基碘化物即使在酸性条件下也能产生高收率。反应性较低的卤化物需要基本介质。在各种未保护的官能团的存在下,反应同样良好地进行。对照实验通过烷基支持S H 2机理。
Fluorinations of ?-Seleno Carboxylic Acid Derivatives with Hypervalent (Difluoroiodo)toluene
作者:Maria A. Arrica、Thomas Wirth
DOI:10.1002/ejoc.200400659
日期:2005.1
A very efficient synthesis of (difluoroiodo)toluene avoiding the use of elemental chlorine and elemental fluorine is described. We have fluorinated a series of α-acceptor substituted selenides using (difluoroiodo)toluene.The reactions are usually very clean and under the reaction conditions no further oxidized products are observed.
titanium enolates of α-seleno esters in the presence of Ph3P or Ph3PO gave the products with high stereoselectivity favoring the syn isomers. Reaction of α-seleno ketones with TiCl4 in the presence of 2 equiv. of Et3N, and subsequently with aldehydes, gave the aldol products with high syn selectivity. The stereoselectivity in the aldol reaction of 3-pentanone also increased by using an excess amount of Et3N
La methylene-6 prostaglandine E 1 est preparee par alkylation de la (4D) [(t-butyldimethylsiloxy)]-4 phenylseleno-2 cyclopentene-2one par un caprate suivie d'une allylation photochimique avec un allylstannane. Son ozonolyse suivie d'une desilylation et d'une hydrolyse donne la oxo-6 prostaglandine E 1 naturelle
La 亚甲基-6 前列腺素 E 1 est preparee par 烷基化 de la (4D) [(t-丁基二甲基甲硅烷氧基)]-4 phenylseleno-2 cyclopentene-2one par un caprate suvie d'une allylation photochimique avec un allylstannane。Son ozonolyse suivie d'une desilylation et d'une 水解 donne la oxo-6 prostaglandine E 1 naturelle