Scope and Utility of a New Soluble Copper Catalyst [CuBr−LiSPh−LiBr−THF]: A Comparison with Other Copper Catalysts in Their Ability to Couple One Equivalent of a Grignard Reagent with an Alkyl Sulfonate
作者:Dennis H. Burns、Jeffrey D. Miller、Ho-Kit Chan、Michael O. Delaney
DOI:10.1021/ja963944q
日期:1997.3.1
THF at 0 °C furnished a new soluble copper catalyst that was highly efficient at coupling primary, secondary, tertiary, aryl, vinyl, and allylic Grignard reagents to primary tosylates and primary Grignard reagents to secondary tosylates and mesylates, all with the use of only 1 equiv of Grignard reagent. The new catalyst was shown to be much more reactive than copper catalysts CuBr and Li2CuCl4 and more
The coupling of primary and secondary unactivated alkyl bromides with alkyl-Grignard reagents was performed in good yields under mild conditions by using a new catalytic system: consisting of cobalt chloride and tetramethylethylenediamine (CoCl2⋅2 LiI, 4 TMEDA). The reaction is very chemoselective since ketone, ester and nitrile functions are tolerated.
Copper-catalyzed cross-coupling of alkylsamarium reagents with alkyl halides
作者:William F. Berkowitz、Yanzhong Wu
DOI:10.1016/s0040-4039(97)00604-7
日期:1997.5
SmI2/HMPA converts alkyl iodides and bromides to alkyl samarium reagents which can be cross-coupled with primary alkyl iodides and bromides and secondary iodides in the presence of Cu(I) halides or Li2CuCl4 at room temperature. The alkylation of primary iodides gives good yields of cross-coupling products with negligible homo-coupling products. The method is especially useful for the small scale cross-coupling
Cross-coupling of alkylhalides with alkyl Grignard reagents proceeds with extremely high TONs of up to 1230000 using a Cu/unsaturated hydrocarbon catalytic system. Alkyl fluorides, chlorides, bromides, and tosylates are all suitable electrophiles, and a TOF as high as 31200 h–1 was attained using an alkyl iodide. Side reactions of this catalytic system, i.e., reduction, dehydrohalogenation (elimination)
使用铜/不饱和烃催化系统,烷基卤化物与烷基格氏试剂的交叉偶联可产生高达1230000的极高TON。烷基氟化物,氯化物,溴化物和甲苯磺酸盐都是合适的亲电子试剂,TOF高达31200 h –1使用烷基碘可以达到目的。在没有添加剂的情况下,该催化体系的副反应即还原,脱卤化氢(消除)和卤代烷的均偶联。看来该反应涉及烷基铜中间体的β-氢消除,从而产生烯烃和Cu-H物种,并且该过程既触发副反应又触发Cu催化剂的降解。形成的Cu–H可能促进歧化反应,从而促进烷基卤化物的还原,从而生成烷烃和Cu–X或Cu(0)的生成,这种歧化可以氧化添加到烷基卤化物中以产生烯烃,在某些情况下还可以是均偶联产物。1,3-丁二烯和苯丙炔等不饱和烃类添加剂通过抑制β-氢的消除在实现高效交叉偶联中起着重要作用,
Azo anions in synthesis. Use of trityl- and diphenyl-4-pyridylmethyl-hydrazones for reductive C–C bond formation from aldehydes and ketones
作者:Jack E. Baldwin、Jeffrey C. Bottaro、Jayant N. Kolhe、Robert M. Adlington
DOI:10.1039/c39840000022
日期:——
The lithium salts for trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl haldies, aldehydes, and ketones) at low temperature to form C-trapped azo compounds; these intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, or alkenes, or alcohols.