Synthesis of Aryl-fused 1,4-Oxazepines and their Oxo Derivatives: A Review

Aryl-fused 1,4-oxazepines and their corresponding oxo derivatives are structural components of a number of compounds exhibiting various biological activity. They were found to be useful as pharmaceuticals, for example as psychoneurotic, antihistaminic and analgesic agents. They are also known for relieving memory dysfunction such as that associated with reduced cholinergic function in Alzheimer's disease. Synthetic methods leading to the aryl-fused 2,3,4,5-tetrahydro-1,4-oxazepines can be classified into two groups. The first includes methods based on direct cyclization of the appropriate open-chain precursors, whereas the second involves methods based on the reduction of intermediate products which are usually adequate aryl-fused 2,3-dihydro-1,4-oxazepines, 4,5-dihydro-1,4-oxazepin-3-ones, 3,4-dihydro-1,4-oxazepin-5-ones, 1,4-oxazepin-3,5-diones. There are only a few methods of synthesis based on the transformation of chromanone. This paper presents a review of a variety of methods of the synthesis of important and potentially pharmacologically active 1,4-oxazepine derivatives.