Enantioselective Alkynylation of Aromatic Aldehydes Catalyzed by a Sterically Highly Demanding Chiral-at-Rhodium Lewis Acid

The enantioselective catalytic alkynylation of aromatic aldehydes is reported using a sterically highly hindered bis-cyclometalated rhodium-based Lewis acid catalyst featuring the octahedral metal as the only stereogenic center. Yields of 58–98% with 79–98% enantiomeric excess were achieved using 1–2 mol % of catalyst. This work complements previous work from our laboratory on the enantioselective alkynylation of 2-trifluoroacetyl imidazoles (<i>Chem. - Eur. J.</i> <b>2016</b>, <i>22</i>, 11977–11981) and trifluoromethyl ketones (<i>J. Am. Chem. Soc.</i> <b>2017</b>, <i>139</i>, 4322–4325) using catalysts with octahedral metal-centered chirality