An effective asymmetric α-phenylation of methylketones with triphenylaluminium in the presence of (+)-benzopyranoisoxazolidine has been developed. The reaction proceeds via the in situ formation of a chiral N-alkoxyenamine and the subsequent diastereoselective nucleophilic phenylation to provide α-phenylated products in moderate to good yields, with high enantioselectivities.
Iron Phosphine Catalyzed Cross-Coupling of Tetraorganoborates and Related Group 13 Nucleophiles with Alkyl Halides
作者:Robin B. Bedford、Peter B. Brenner、Emma Carter、Jamie Clifton、Paul M. Cogswell、Nicholas J. Gower、Mairi F. Haddow、Jeremy N. Harvey、Jeffrey A. Kehl、Damien M. Murphy、Emily C. Neeve、Michael L. Neidig、Joshua Nunn、Benjamin E. R. Snyder、Joseph Taylor
DOI:10.1021/om500518r
日期:2014.10.27
Iron phosphinecomplexes prove to be good precatalysts for the cross-coupling of alkyl, benzyl, and allyl halides with not only aryl triorganoborate salts but also related aluminum-, gallium-, indium-, and thallium-based nucleophiles. Mechanistic studies revealed that while Fe(I) can be accessed on catalytically relevant time scales, lower average oxidation states are not formed fast enough to be relevant
By the nucleophilic phenylation of O‐silyl N,O‐ketene acetals, generated in situ from N‐alkoxy amides, a phenyl group can be introduced onto the α‐carbon atom of amides through N−O bond cleavage in a two‐step, one‐pot process. The asymmetric synthesis of α‐aryl amides through the diastereoselective arylation of a chiral N,O‐ketene acetal is also described.
Nucleophilic α-Arylation and α-Alkylation of Ketones by Polarity Inversion of N-Alkoxyenamines: Entry to the Umpolung Reaction at the α-Carbon Position of Carbonyl Compounds
N‐alkoxyenamines from ketones has led to an efficient umpolung reaction. The alkylation of N‐alkoxyenamines with trialkylaluminum compounds proceeded smoothly and gave α‐alkylated ketones (see scheme). This reaction offers a simple transformation of ketones into α‐substituted ketones without the need to isolate enamines and intermediary imines.
Rhodium-Catalyzed Cross-Coupling of Vinylarenes with Arylaluminum Reagents in the Presence of Ketones
作者:Shota Tanaka、Atsunori Mori
DOI:10.1002/ejoc.201301757
日期:2014.2
in the presence of the chloro(1,5-cyclooctadiene)rhodium(I) dimer, [RhCl(cod)]2, and diisopropylketone (2,4-dimethyl-3-pentanone) as an additive occurred to give (E)-stilbene in quantitative yield. The use of other arylaluminum reagents afforded β-arylated products in good to excellent yields. This reaction was found to be promoted by ketones as additives, which are reduced to the corresponding alcohols
实现了芳基铝试剂与乙烯基芳烃的铑催化加成/消除以获得二苯乙烯衍生物。在氯(1,5-环辛二烯)铑(I)二聚体、[RhCl(cod)]2 和二异丙基酮(2,4-二甲基-3-戊酮)存在下二乙基(苯基)铝与苯乙烯的反应) 作为添加剂发生以定量收率产生 (E)-二苯乙烯。使用其他芳基铝试剂以良好至极好的收率提供 β-芳基化产物。发现该反应被作为添加剂的酮促进,酮被还原为相应的醇,如通过 1 H NMR 光谱分析粗反应混合物所证实的。