Acyl migration from N to C in aziridine-2-carboxylic esters

DBU-promoted carboxylative cyclization of o-hydroxy- and o-acetamidoacetophenone

“…A likely mechanism for the carboxylative cyclization of o -acetamidoacetophenone with carbon dioxide is proposed as shown in Scheme 1 . The reaction can evolve along two pathways: in path A , deprotonation of o -acetamidoacetophenone by DBU gives enolate I , which undergoes an acyl migration from nitrogen to carbon [ 25 – 26 ] similar to the Baker–Venkataraman O to C acyl migration [ 27 ]. After a proton shift from the enol to nitrogen, the resultant intermediate III is carboxylated with carbon dioxide in the presence of DBU to afford intermediate IV , which subsequently undergoes a cyclization reaction to give V .…”

An Easy Route to Aziridine Ketones and Carbinols

“…Tetrahydrofuran was distilled from Na/benzophenone. Esters 1a and 1b were prepared according to the literature from aziridine-2-carboxylate in reactions with Boc-anhydride [ 22 ] and trityl-chloride [ 23 ], respectively. Ester 1c was obtained in the reaction of benzyl aziridine-2-carboxylate with Boc-anhydride [ 23 ].…”

Synthesis of Unnatural α-Amino Acids from (Pyridin-2-yl) Carbamate via CIPE-Induced Carbonyl Migration

“…Inspired by our previous study on the rearrangement of 2-pyridyl ethers, herein we report a convenient strategy for the synthesis of unnatural amino acids via the intramolecular rearrangement of carbamates, which are readily available from amines and their common protecting groups, such as Boc anhydride or chloroformates, etc. Even though carbonyl migration has been observed in very specific cases, a few reports were found for the synthesis of amino acids with an inactivated starting material, while Boc-protected α-amino organolithium was reported to be stable at −78 °C . In this work, we introduced a 2-pyridyl group to trigger the deprotonation via complex-induced proximity effect (CIPE), which was followed by the migration of the carbonyl group to provide new amino acid skeletons (Scheme d).…”