Directα-alkylation of unactivatedketones using benzylic alcohols as electrophiles has been achieved at room temperature. This reaction takes place via in situ formed acetal using triflic acid and trimethyl orthoformate. It is believed that methyl vinyl ether formed from the in situ generated dimethyl acetal in the presence of triflic acid undergoes alkylation. Diverse ketones could be alkylated with
Ligand-Free Nickel-Catalysed 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds
作者:Wen Chen、Lu Sun、Xi Huang、Jiayi Wang、Yanqing Peng、Gonghua Song
DOI:10.1002/adsc.201400761
日期:2015.5.4
catalytic system has been developed for the 1,4‐addition of arylboronic acids to α,β‐unsaturatedcarbonylcompounds. With catalyst loadings of 1–2 mol%, a series of 1,4‐adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5–30 min under a nitrogen atmosphere and microwave irradiation. The 1,4‐addition of arylboronic acids to acrylates is less efficient.
A practically simple and direct α‐alkylation of unactivatedketones using benzylic alcohols has been achieved. The in situ formed acetals are the key for the success of the reaction. The catalyst, silver hexafluoroantimonate(V) (AgSbF6) provides double activation by converting the ketone into an enol ether via acetal and generation of carbocationic center at the benzylic position of the benzylic alcohol