New catalytic methods for carbon-nitrogen bond formation are important for their broad applications in organic synthesis, especially for pharmaceuticals and natural products.  Organocatalytic C-N bond formations that avoid the use of toxic and expensive metal catalysts are particularly challenging. We report here a novel method for C-N bond formation by the reaction of a,b-unsaturated aldehydes with nitrosobenzene using N-heterocyclic carbene (NHC) catalysis, forming isoxazolidin-5-ones that are further converted to the corresponding N-p-methoxyphenyl (N-PMP) protected b-amino acid esters by an acid-catalyzed Bamberger-like rearrangement in a mild one-pot synthetic protocol.  A variety of aryl- and alkyl-substituted a,b-unsaturated aldehydes (1a–1h) were found to form the isoxazolidin-5-ones (3a–3h) and the corresponding b-amino esters (4a–4h) by this method. Substrates with different functional groups, such as ether, ester, nitro and sulfonate, were readily accommodated in this protocol.