There are a number of papers that have described catalytic asymmetric C-H insertion reactions (see a recent review on catalytic intramolecular C-H aminations by Davies & Long), but there are only a few examples of asymmetric O-H insertion reactions. In the ASAP section of the Journal of the American Chemical Society, Maier & Fu reported the first “effective” method for catalytic enantioselective insertions into O-H bonds.
The authors showed that in the presence of copper and a chiral bisazaferrocene ligand, various alcohols reacted with methyl alpha-diazo-alpha-phenylacetate, yielding alpha-alkoxy esters (the best yields and ee were achieved using methanol, 2-trimethylsilylethanol, or para-methoxybenzyl alcohol). They further explored the scope of the reaction involving 2-trimethylsilylethanol and demonstrated that they could isolate a range of alpha-diazo-alpha-arylacetates in high yields and ee – since the trimethylsilylethyl group can be easily removed using boron trifluoride diethyl etherate, the authors could also obtain enantiomerically pure alpha-hydroxy esters in high yields and ee.
Joshua Finkelstein (Associate Editor, Nature)