Treatment of N-arylmethyl-N-methyl-cis-3-phenylsulfanyl acrylamide (5) with p-toluenesulfonic acid induced two reactions; cyclization to 1,2-dihydrobenz[c]azepin-3-ones (7) and N-dearylmethylation to N-methylacrylamides (9 and 10) depending on the structures of the substrates. The route provides a simple method of preparing 6-methoxy-(7e), 8-methoxy-(7d), 6,8-dimethoxy-(7f), and 8,9-dimethoxy-N-methyl-1,2-dihydrobenz[c]azepin-3-ones (7g), although the scope is limited by some side reactions.
The Synthesis of Annulated Azepin-3-one Derivatives from 1,3,4-Pentatrienyl Nitrones by a Heterocyclization−Rearrangement Sequence
6 with potassium hydroxide or sodiummethoxide in methanol at room temperature provides 1,2-dihydro[c]benzazepin-3-ones 9. The high product yields and the ease of the reactions under surprisingly mild conditions are particularly intriguing in view of the complex mechanistic pathway involved in the overall transformation. A mechanism based on a multistep rearrangement is proposed, involving conjugated
Dihydro[<i>c</i>]benzazepin-3-ones via Conjugated Nitrone−Allene Precursors
作者:Karin Knobloch、Wolfgang Eberbach
DOI:10.1021/ol0056832
日期:2000.4.1
[formula: see text] Treatment of o-propargylaryl nitrones with base provided 1,2-dihydro[c]benzazepin-3-ones in good yields. The straightforward transformation is explained on the basis of a multistep rearrangement involving conjugated allene-nitrones as precursors of a 1,7-dipolar electrocyclization process that is followed by further bond reorganizations.