作者:Chao Li、Jie Wang、Lisa M. Barton、Shan Yu、Maoqun Tian、David S. Peters、Manoj Kumar、Antony W. Yu、Kristen A. Johnson、Arnab K. Chatterjee、Ming Yan、Phil S. Baran
DOI:10.1126/science.aam7355
日期:2017.6.9
functionalized alkyl boronate esters from abundant carboxylic substituents. This broad-scope nickel-catalyzed reaction uses the same activating principle as amide bond formation to replace a carboxylic acid moiety with a boronate ester. Application to peptides allowed expedient preparations of α-amino boronic acids, often with high stereoselectivity, thereby facilitating synthesis of the alkyl boronic acid drugs
Stereocontrolled Total Synthesis of (−)-Stemaphylline
作者:Ana Varela、Lennart K. B. Garve、Daniele Leonori、Varinder K. Aggarwal
DOI:10.1002/anie.201611273
日期:2017.2.13
to CHCl3, efficient 1,2‐metalate rearrangement of the intermediate boronate occurs with both halide and ester leaving groups. The methodology was used in the total synthesis of the Stemona alkaloid (−)‐stemaphylline in just 11 steps (longest linear sequence), with high stereocontrol (>20:1 d.r.) and 11 % overall yield. The synthesis also features a late‐stage lithiation–borylation reaction with a tertiary
即使使用良好的离去基团 (Cl - ),容易获得的 α-硼基吡咯烷与金属类胡萝卜素的同系化也特别具有挑战性。通过进行从 Et 2 O 到 CHCl 3 的溶剂转换,中间体硼酸酯与卤化物和酯离去基团发生有效的 1,2-金属盐重排。该方法用于百部生物碱 (−)-Stemaphylline 的全合成,仅需 11 个步骤(最长的线性序列),具有高立体控制(>20:1 dr)和 11% 的总产率。该合成还具有与含类胡萝卜素的叔胺进行后期锂化-硼化反应的特点。
Studies on the Lithiation, Borylation, and 1,2‐Metalate Rearrangement of
<i>O</i>
‐Cycloalkyl 2,4,6‐Triisopropylbenzoates
作者:Rory C. Mykura、Pradip Songara、Eugenia Luc、Jack Rogers、Ellie Stammers、Varinder K. Aggarwal
DOI:10.1002/anie.202101374
日期:2021.5.10
have not. We have studied the use of cyclic TIB esters in lithiation‐borylation reactions and looked at the effect of ringsize (3‐ → 6‐membered rings) on the three key steps of the lithiation‐borylation protocol: deprotonation, borylation and 1,2‐metalate rearrangement. Although all ringssizes could be deprotonated, the cyclohexyl case was impractically slow, and the cyclopentyl example underwent α‐elimination
α-Functionalization of alkyl boronicesters and homologation of aryl boronicesters by regioselective radical C(sp3)–H activation in boron-ate complexes is reported. Reaction of commercial or readily accessed aryl boronic acid pinacol esters with alkyl lithium reagents provides boron-ate complexes. Selective α-C–H abstraction by in situgenerated trifluoromethyl radicals leads to radical anions that
Photoredox‐Catalyzed Cyclobutane Synthesis by a Deboronative Radical Addition–Polar Cyclization Cascade
作者:Chao Shu、Adam Noble、Varinder K. Aggarwal
DOI:10.1002/anie.201813917
日期:2019.3.18
single‐electron transfer induced deboronative radicaladdition to an electron‐deficient alkene followed by single‐electron reduction and polar 4‐exo‐tet cyclization with a pendant alkyl halide. Key to the success of the methodology was the use of easily oxidizable arylboronate complexes. Structurally diverse cyclobutanes are shown to be conveniently prepared from readily available alkylboronic esters and