Stereochemical modulation of ketyl radical cyclization enabled by pyridine-boryl radicals: catalytic diastereoselective synthesis of trans -2-alkyl-1-indanols.

Previously available ketyl radical cyclization conditions suffer from low and uncontrollable diastereoselectivity because of the absence of reagent-substrate interactions. In this report, stereochemical modulation was accomplished by taking advantage of the pyridine-boryl radical, which leaves the synthetically modifiable boronate moiety on the carbonyl oxygen near the reacting center during the stereo-determining cyclization step. In consequence, a catalytic diastereoselective synthesis of trans -2-substituted-1-indanols was achieved in the presence of a sterically congested six-membered diboronic ester and an efficient hydrogen atom donor.