Rhodium-catalyzed hydroacylation chemistry, though currently limited to the synthesis of 5-membered rings, offers a potential route to medium rings (7 to 11 atoms) through the use of chelating substrates. Chelating substrates containing a Lewis basic tethering atom (N or O) are expected to allow for the synthesis of medium rings without requiring the formation of large metallacycles as intermediates. Instead, the tridentate substrates will yield reaction intermediates that contain two small metallacycles (Scheme). The individual metallacycles are very similar to those formed during hydrocarbonylation of aminoalkenes, a reaction known to tolerate metallacycles ranging from 5 to 7 atoms.

We have prepared several test substrates and are currently screening a variety of rhodium complexes as potential catalysts for the hydroacylation reaction. A few of our test substrates are shown here.