通过使用NiBr(2)·二甘醇二甲醚原位形成的催化剂和pybox配体(两者均可商购),我们实现了未活化叔烷基亲电试剂偶联反应的第一个实例,并取得了首次成功镍催化偶联产生除 CC 键以外的键。具体来说,我们已经确定,这种催化剂在温和条件下完成了未活化的叔、仲和伯烷基卤化物与二硼试剂的宫浦型硼酸化反应,以提供烷基硼酸酯,这是一个具有实质性(并扩大)效用的化合物家族;事实上,叔烷基溴的 umpolung 硼酸化可以在低至 -10 °C 的温度下实现。该方法表现出良好的官能团兼容性和区域特异性,这两者都可能是合成烷基硼酸酯的传统方法的问题。与看似相关的镍催化 CC 键形成过程相反,在这种镍催化的 CB 键形成反应中,叔卤化物比仲卤化物或伯卤化物更具反应性;鉴于两种转化都可能遵循氧化加成的内球电子转移途径,这种差异尤其值得注意。
Manganese-Catalyzed Borylation of Unactivated Alkyl Chlorides
作者:Thomas C. Atack、Silas P. Cook
DOI:10.1021/jacs.6b03157
日期:2016.5.18
of (bis)pinacolatodiboron with a wide range of alkyl halides, demonstrating the first manganese-catalyzed coupling with alkyl electrophiles. This method allows access to primary, secondary, and tertiary boronic esters from the parent chlorides, which were previously inaccessible as coupling partners. The reaction proceeds in high yield with as little as 1000 ppm catalyst loading, while 5 mol % can
Metal catalyst-free photo-induced alkyl C–O bond borylation
作者:Guobin Ma、Changzhou Chen、Sangita Talukdar、Xinluo Zhao、Chuanhu Lei、Hegui Gong
DOI:10.1039/d0cc04776g
日期:——
Metal catalyst free, blue visible light-induced C–O bond borylation of unactivated tertiary alkyl methyl oxalates has been developed to furnish tertiary alkyl boronates. From the secondary alcohols activated with imidazolylthionyl, moderate yields of boronates were attained under standard photo-induced conditions. Preliminary mechanisticstudies confirmed the involvement of a (DMF)2–B2cat2 adduct that
iron-catalyzed cross-electrophile coupling of aryl chlorides with unactivated alkylchlorides via an iron/B2pin2 catalytic system has been developed. (Hetero)aryl chlorides undergo this transformation smoothly under mild conditions, furnishing the alkylated products with good efficiency. This protocol features excellent functional group compatibility and gram-scale synthesis, which also enables the late-stage functionalization