Asymmetric C-C bond formation via the diastereoselective aza-Claisen rearrangement of N-allylketene N,O-acetal 1 is described. Diastereoselection noted for rearrangement 1 → 2 ranges from 84% to 96% and is a consequence of complete (Z)-N,O-acetal olefin selectivity in 1, high Cα-si-face selectivity in the rearrangement of 1 to 2, and the absence of Cα epimerization in oxazoline 2. Experiments which establish the steric bulk of the C4 appendage as a particularly important variable are also reported. Acid-catalyzed hydrolysis of rearranged oxazoline 2 completes an efficient, enantioselective synthesis of 2-substituted pent-4-enoic acid 4 and regenerates for recycling the chiral auxiliary reagent 3, initially prepared from inexpensive α-amino acids.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of the American Chemical Society|
|State||Published - 1985|
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