Stereospecific Synthesis of 2‐Oxazinyl‐4‐oxoazetidinecarbamates Starting from a 1,2‐Diazepine. A new type of intramolecular transbenzoylation

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Abstract
Azeitidinodiazepines4band4creact with acylnitroso dienophiles5a–c, specifically from their convexe α‐side, but in a non‐regiospecific way, leading thereby stereospecifically to the expected adducts6a–dand7a–d. The three‐dimensional structures of6aand7awere determined by X‐ray analyses which corroborated their NMR data. OsO4cis‐glycolization occurred in good yield with the inverse adducts7aand7eand led to the rearranged products10. These latter ones result from an intramolecular N‐ to O‐transbenzoylation of the short‐lived intermediates9followed by fragmentation of the animal function. X‐Ray analysis of7ashowed the N(10) atom to be pyramidal, a result which demonstrates that it does not have any pronounced benzamide character; otherwise no such N‐ to O‐transbenzoylation would have taken place. Structure and relative configuration of10awere ascertained by X‐ray analysis which confirmed its NMR data as well as the stereochemical outcome of its formation.