A variety of ortho,ortho'-disubstituted hydrobenzoin derivatives are readily accessible through a directed ortho,ortho'-dimetalation strategy in which the alcohol functions in hydrobenzoin are deprotonated by n-BuLi and the resulting lithium benzyl alkoxides serve as directed metalation groups. The optimization and scope of this reaction are discussed, and the utility of this process is demonstrated in the one-pot preparation of a number of chiral diols as well as a short synthesis of the chiral ligand Vivol.
through a sequence of rapid single-electron oxidation/[4+4] cyclization from 2,2′-disubstituted stilbene. The antarafacial manner of the thermally allowed [4+4] cyclization was further proven by series of control experiments and density functional theory calculations. Our findings provide an important addition to the aerobic copper-catalyzedoxidativecyclization.
Aerobic oxidative cyclization of 2,2′-dihydroxystilbenes via oxygen cation radical to give cis-4b,9b-dihydrobenzofuro[3,2-b]benzofurans was carried out in an enantioselective manner (up to 89% ee) by using (nitrosyl)Ru(salen) 10 as the catalyst under photo-irradiated conditions.
Bidirectional Metalation of Hydrobenzoin: Direct Access to New Chiral Ligands and Auxiliaries
作者:Inhee Cho、Labros Meimetis、Robert Britton
DOI:10.1021/ol900323u
日期:2009.5.7
A bidirectional ortho metalation of the readily available chiral diol hydrobenzoin has been developed that provides direct access to new ortho-functionalized hydrobenzoin derivatives. This one-pot procedure should broaden the utility of hydrobenzoin as an auxiliary and ligand in asymmetric synthesis.
Reduction of o-hydroxybenzaldehydes by aqueous titanium trichloride. A new route to 2-(benzofuran-2-yl)phenols