Michael R. Tracey

(4R)-3-Allenyl-4-(diphenylmethyl)-oxazolidin-2-one, an unsubstituted allenamide

The first X-ray structure of an unsubstituted allenamide, C(19)H(17)NO(2), is reported. The solid-state phase supports the notion that a key minimum conformation of allenamides can be invoked to rationalize the observed stereochemical outcomes in many of our methodological studies employing allenamides. This minimum conformation involves two important factors, i.e. having approximate coplanarity between the planes of the oxazolidinone ring and the internal olefin, and having the allene moiety facing away from the carbamate carbonyl group. The C-N-C=C torsion angle that quantifies this approximate coplanarity between the plane of the oxazolidinone ring and that of the internal olefin, as determined from this crystallographic study, is -19.1 (2) degrees . A minimized structural calculation, which determined this angle to be -16.1 degrees , is in close agreement. Additional structural features include a probable pi-pi interaction between the allene moiety and a benzene ring, and non-classical hydrogen bonding in the form of weak C-H...O interactions that are responsible for the formation of two-dimensional networks.