Bicycles fused

Scheme 6.272 Preparation of bicyclic fused azepinones by intramolecular transamidation.

Selective Reduction of the O-N-O Fragment in Cyclic and Bicyclic Fused Nitroso Acetals From the point of development of methodology of organic synthesis, selective reduction of the nitroso acetal fragment and associated processes are the most important reactions of nitroso acetals (also see Scheme 3.154). 

These studies were carried out for hve-membered monocyclic TV-alkoxy-(406-408) and /V-siloxyisoxazolidines (178) (A), for iV-siloxytetrahydro-4// -oxazines (274), and bicyclic fused derivatives containing the isoxazolidine ring (B) (99, 157, 337). 

An alternative approach to 5-5 bicyclic fused ring systems utilizing a condensation reaction was described by Moderhack et al. <2000JPC591> (Scheme 10). The amino-substituted tetrazole derivatives 52 and 54 gave the neutral 53 as well as the mesoionic derivatives 55 in moderate to excellent yields (16-86% R = CH3 or Ph). 

Zemplen s work was revisited by Bromund et al43 by exploring the reaction in diverse aldose series (D-galacto, D-xylo, L-arabino). Similar bicyclic fused structures of OZT on pyran backbones were proposed (Scheme 20). 

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