期刊
CHEMICAL SCIENCE
卷 13, 期 20, 页码 5973-5981出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/d2sc00800a
关键词
-
资金
- SURSUMCAT Raising up Catalysis for Innovative Developments [20174SYJAF]
- University of Bologna
- Chiesi Farmaceutici S.p.A.
A highly diastereoselective pinacol coupling reaction of aromatic aldehydes has been achieved by using a red-absorbing organic dye in the presence of a redox-active titanium complex. The reaction showed complete selectivity for the D,L diastereoisomer and high enantiocontrol.
The pinacol coupling reaction, a reductive coupling of carbonyl compounds that proceeds through the formation of ketyl radicals in the presence of an electron donor, affords the corresponding 1,2-diols in one single step. The photoredox version of this transformation has been accomplished using different organic dyes or photoactive metal complexes in the presence of sacrificial donors such as tertiary amines or Hantzsch's ester. Normally, the homo-coupling of such reactive ketyl radicals is neither diastereo- nor enantio-selective. Herein, we report a highly diastereoselective pinacol coupling reaction of aromatic aldehydes promoted by 5 mol% of the non-toxic, inexpensive and available Cp2TiO2 complex. The key feature that allows the complete control of diastereoselectivity is the employment of a red-absorbing organic dye in the presence of a redox-active titanium complex. Taking advantage of the well-tailored photoredox potential of this organic dye, the selective reduction of Ti(iv) to Ti(iii) is achieved. These conditions enable the formation of the D,L (syn) diastereoisomer as the favored product of the pinacol coupling (d.r. > 20 : 1 in most of the cases). Moreover, employing a simply prepared chiral SalenTi complex, the new photoredox reaction gave a complete diastereoselection for the D,L diastereoisomer, and high enantiocontrol (up to 92% of enantiomeric excess).
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据