Oxazepane-5,7-dione

In addition to their formation by transformation of smaller ring heterocycles, oxazepines are capable of contraction as demonstrated by the carbene transformation of the oxazepane dione (97) in the presence of catalytic amounts of copper or rhodium to the dihydropyrrolone (98) by loss of C02 <95AG(K)78)>. 

Oxindoles 112, substituted at N-1 by an electron-withdrawing group and at C-3 by an CO-amino chain, underwent isomerization at ambient temperature to form l,4-oxazepan-3,7-diones 113 that contain a quaternary asymmetric carbon bearing a 2-aminophenyl residue (14JOC10945). 

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