Regioselectivity in nickel(0) catalyzed cycloadditions of carbon dioxide with diynes
作者:Thomas N. Tekavec、Atta M. Arif、Janis Louie
DOI:10.1016/j.tet.2004.06.025
日期:2004.8
The regioselectivity of Ni(0)-catalyzed cycloadditions of CO2 (1 atm) with various asymmetrical diynes to afford pyrones was explored. The use of 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) provided high regioselectivity when one terminal substituent on the diyne was a methyl group and the other was medium or large in size (RL=i-Pr, t-Bu, or TMS). In contrast, the use of a relatively small
探索了Ni(0)催化的CO 2(1 atm)与各种不对称二炔提供吡喃酮的环加成反应的区域选择性。当二炔上的一个末端取代基为甲基,另一个末端为中等或大尺寸时,使用1,3-双-(2,6-二异丙基苯基)-咪唑-2-亚烷基(IPr)具有很高的区域选择性(R L = i -Pr,t -Bu或TMS)。相比之下,仅当R L大(TMS)时,使用相对较小的N杂环卡宾1,3-二甲基咪唑-2-亚烷基(IMes)才具有较高的选择性。主要异构体的X-射线晶体分析表明,相对大ř大号组在所述吡喃酮的3-位。