1.2- Oxazepines Meisenheimer rearrangement

The Meisenheimer rearrangement of tertiary amine N- oxides has been applied to the synthesis of both monocyclic 1,2-oxazepines, e.g. (309) (65JOC3135, 65JCS1653, 82H(19)173), and those fused to benzene (80AJC833) and a variety of heterocyclic rings (80AJC1335). 

Compared with azepine derivatives, considerable scope still exists for innovative exploration of ring-closing metathesis methodology to access multisubstituted 1,2-oxazepine and 1,3-thiazepine derivatives and benz-fused analogues. Also, the full synthetic potential of the Meisenheimer rearrangement to afford various 1,2-oxazepine derivatives with different types of functionality present is still to be realized. 

A new route to the 12(S)carba-eudistomin skeleton was developed by T. Kurihara et al. The key substrate for this new route was a 1,2-c/s-2-ethenylazetopyridoindole, which was readily oxidized at 0 °C to afford the corresponding A/-oxide. This A/-oxide spontaneously underwent a [2,3]-Meisenheimer rearrangement to afford the desired oxazepine derivative. Interestingly, when the 1,2-frans-2-ethenylazetopyridoindole was subjected to identical conditions, the [1,2]-Meisenheimer rearrangement occurred exclusively and gave rise to an isoxazolidine derivative. 

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