Jin Yonghoon, Lee Junseok, Jo Woohyun, Yu Jeongwoo, Cho Seung Hwan
Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.
Institute for Convergence Research and Education in Advanced Technology (I-CREATE), Yonsei University, Seoul, 03722, Republic of Korea.
Nat Commun. 2024 Oct 25;15(1):9239. doi: 10.1038/s41467-024-53606-6.
Axially chiral allenes bearing organoboron groups are highly sought-after building blocks in organic synthesis due to their potential for generating a wide range of axially and centrally chiral molecules. However, the existing methods for preparing axially chiral allenes containing boron group are primarily limited to the synthesis of allenyl boronic esters, and strategies for accessing axially chiral homoallenyl boronic esters are still scarce. Here, we report the general method for synthesizing axially chiral α-boryl-homoallenyl boronic esters through a highly regio- and stereoselective copper-mediated S2'-addition of newly prepared (diborylalkyl)copper species to chiral propargyl electrophiles. The reaction conditions were optimized to achieve high yields and excellent stereospecificity. The obtained products were successfully transformed into various axially chiral allenes and other chiral molecules by transforming diboron units. The potential for axial-to-central chirality transfer of axially chiral α-boryl-homoallenyl boronic esters is also demonstrated through the stereospecific addition to aldehydes and N-H aldimines, yielding enantioenriched 1,2-oxaborinin-3,5-dienes and 2-aminomethyl-1,3-dienes.
由于具有生成多种轴向和中心手性分子的潜力，带有有机硼基团的轴手性联烯是有机合成中备受追捧的结构单元。然而，现有的制备含硼基团的轴手性联烯的方法主要局限于烯丙基硼酸酯的合成，而获得轴手性高烯丙基硼酸酯的策略仍然很少。在此，我们报道了一种通用方法，通过新制备的（二硼烷基）铜物种与手性炔丙基亲电试剂进行高度区域和立体选择性的铜介导S2'-加成反应，合成轴手性α-硼基高烯丙基硼酸酯。对反应条件进行了优化，以实现高产率和优异的立体专一性。通过转化二硼单元，所得产物成功转化为各种轴手性联烯和其他手性分子。轴手性α-硼基高烯丙基硼酸酯从轴向手性向中心手性转移的潜力也通过对醛和N-H醛亚胺的立体专一性加成得到证明，生成对映体富集的1,2-氧硼杂环戊烷-3,5-二烯和2-氨基甲基-1,3-二烯。
