Synthesis and Rh-catalyzed reductive cyclization of 1,6-enynes and 1,6-diynes containing alkynylboronate termini
作者:Christopher J. Pell、Oleg V. Ozerov
DOI:10.1016/j.jorganchem.2020.121143
日期:2020.4
Ir-catalyzed dehydrogenative borylation of terminal alkynes (DHBTA) has been used to borylate the C(sp)-H bond in a series of 1,6-enynes and 1,6-diynes. Ir catalysts based on the diarylamido/bis(phosphine) PNP ligands proved to be capable of performing DHBTA on these substrates. The alkynylboronate products were then explored as substrates in reductive cyclization reactions designed to yield five-membered carbocycles
末端炔烃的Ir催化脱氢硼化(DHBTA)已用于在一系列1,6-炔和1,6-二炔中使C(sp)-H键硼化。基于二芳基酰胺/双(膦)PNP配体的Ir催化剂被证明能够在这些底物上进行DHBTA。然后将炔基硼酸酯产物作为还原环化反应的底物进行研究,该反应旨在生成五元碳环和杂环并保留碳-硼键。H 2对烯炔的还原环化使用由双齿膦配体支撑的阳离子Rh催化剂(在Krische等人的工作之后)进行,其中BINAP被证明是性能最佳的。硼化的烯炔的还原环化通常产生异构产物的混合物。优化硼化的1,6-烯炔的还原环化以产生单一产物的尝试没有成功;此外,在这些反应中产物的分布很难再现。另一方面,使用相同的Rh催化剂进行1,6-二炔的还原环化效果更好,从而实现了选择性和重现性。特别地,双(炔丙基)胺的炔基硼酸酯衍生物经历平滑的还原环化成3,4-取代的吡咯。