Copper complexes generated in situ from CuCl2, alkylGrignardreagents, and 1,3‐dienes play important roles as catalytic active species for the 1,2‐hydroalkylation of 1,3‐dienes by alkylfluorides through CF bond cleavage. The alkyl group is introduced to an internal carbon atom of the 1,3‐diene regioselectively, thus giving rise to the branched terminal alkene product.
Reaction of 1,1-dibromoalkane (R1CHBr2) with trialkylzincate ((R2)3ZnLi) followed by a palladium catalyzed coupling reaction of the resulting secondary organozinc reagent (R1CH(R2)ZnL) with various electrophiles (El-X) afforded R1CH(R2)El.
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,
Copper-Catalyzed Cross-Coupling Reaction of Grignard Reagents with Primary-Alkyl Halides: Remarkable Effect of 1-Phenylpropyne
作者:Jun Terao、Hirohisa Todo、Shameem Ara Begum、Hitoshi Kuniyasu、Nobuaki Kambe