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 (Chem. - Eur.
J. 2016, 22, 11977–11981)
and trifluoromethyl ketones (J. Am. Chem. Soc. 2017, 139, 4322–4325) using catalysts
with octahedral metal-centered chirality.