A useful ring transformation route to novel thiazepino[7,6-b]indoles from monochloro-beta-lactam-fused 1,3-thiazino[6,5-b]indoles, analogues of cyclobrassinin

作者：Csomos Peter; Fodor Lajos^*; Csampai Antal; Sohar Pal^*

来源：Tetrahedron, 2017, 73(17): 2476-2482.

DOI：10.1016/j.tet.2017.03.047

• Staudinger cycloaddition
• beta-Lactam
• Ring transformation
• Indole protection
• Thiazepino[7,6-b]indoles

The Staudinger ketene-imine cycloaddition reactions of cyclobrassinin phytoalexin analogues 2-aryl-4,9-dihydro-1,3-thiazino[6,5-b]indoles with chloroacetyl chloride as a ketene source were investigated under different conditions. Both beta-lactam ring formation and the N-chloroacetylation of the indole moiety took place. The indole N-chloroacetyl group can be easily removed by treatment in the presence of silica gel in methanol at reflux temperature. The selective beta-lactam formation can be also achieved in certain cases under milder Staudinger conditions. The treatment of azeto[2,1-b]thiazino[6,5-b]indole-1-one derivatives with sodium ethoxide in ethanol provided the novel thiazepino[7,6-b]indole ring systems in a one-step ring transformation. The structures of the new ring systems were determined by means of IR and NMR spectroscopy.

• 出版日期2017-4-27