Hydride as a Leaving Group in the Reaction of Pinacolborane with Halides under Ambient Grignard and Barbier Conditions. One-Pot Synthesis of Alkyl, Aryl, Heteroaryl, Vinyl, and Allyl Pinacolboronic Esters
作者:Jacob W. Clary、Terry J. Rettenmaier、Rachel Snelling、Whitney Bryks、Jesse Banwell、W. Todd Wipke、Bakthan Singaram
DOI:10.1021/jo201093u
日期:2011.12.2
addition of pentane to the reaction mixture. DFT calculations (Gaussian09) at the B3LYP/6-31G(d) level of theory show that disproportionation of HMgBr to MgH2 and MgBr2 is viable in the coordinating ethereal solvents. This reaction also can be carried out under Barbier conditions, where the neat PinBH is added to the flask prior to the in situ formation of Grignard reagent from the corresponding organic
格氏试剂(脂族,芳族,杂芳族,乙烯基或烯丙基)与1当量的4,4,5,5-四甲基-1,3,2-二氧杂硼烷(pinacolborane,PinBH)在环境温度下在四氢呋喃(THF)中反应为提供相应的频哪醇硼酸酯。最初形成的二烷氧基烷基硼氢化物中间体可快速消除溴化氢化镁(HMgBr),并以非常好的收率提供硼酸酯产品。在将戊烷加入到反应混合物中之后,溴化氢溴化铵(HMgBr)歧化为氢化镁(MgH 2)和溴化镁(MgBr 2)的1:1混合物。在B3LYP / 6-31G(d)理论水平上的DFT计算(Gaussian09)显示,HMgBr歧化为MgH 2和MgBr 2在配位醚溶剂中是可行的。该反应也可以在Barbier条件下进行,其中在从相应的有机卤化物和镁金属原位形成格氏试剂之前,将纯净的PinBH加入到烧瓶中。在Barbier条件下合成萘酚硼酸酯不能从反应性卤化物(例如苄基和烯丙基卤化物)中产生W