Rethinking Hydrolytic Imidazoline Ring Expansion: A Common Approach to the Preparation of Medium-Sized Rings via Side-Chain Insertion into [1.4]Oxa- and [1.4]Thiazepinone Scaffolds
datasetposted on 19.12.2018, 00:00 by Elena Reutskaya, Angelina Osipyan, Alexander Sapegin, Alexander S. Novikov, Mikhail Krasavin
The previously reported ring-expansion strategy involving hydrolytically prone imidazoline rings was thought to include the formation of a hydrated imidazoline intermediate. In this work, we accessed the latter via the addition of a 2-aminoethyl side chain onto a lactam moiety. This led to an efficient three-atom ring expansion of diarene-fused [1.4]oxazepines and [1.4]thiazepines and led us to propose to term this common approach the hydrated imidazoline ring expansion (HIRE) reaction. The strategy was extended to the insertion of longer (containing up to five atoms) side chains, and thus, larger (11- to 12-membered) diarene-fused rings were obtained via the homo-HIRE and homo2-HIRE reactions, respectively. This underscores the utility of the HIRE reaction for the preparation of medium-sized rings, an important class of chemical tools for interrogation of various biological targets.
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HIRE reactionsimidazoline ring expansiondiarene-fused ringshomo 2HIRE reactionSide-Chain InsertionMedium-Sized RingsRethinking Hydrolytic Imidazoline Ring Expansionside chains2- aminoethyl side chainlactam moietythree-atom ring expansionchemical toolsCommon Approachimidazoline ringsring-expansion strategy12- membered