Synthesis and thermal stability of some 1-benzothiepins

✍ Scribed by Ichiro Murata; Toshio Tatsuoka

• Book ID: 104215121
• Publisher: Elsevier Science
• Year: 1975
• Tongue: French
• Weight: 224 KB
• Volume: 16
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)75217-8

✦ Synopsis

We have recently developed a novel approach to the synthesis of thermally labile 1-benzothiepin (ljl) based on the rhodium complex promoted isomerisation of 4,5-benzo-3-thiatricyclo[4.1.0.02'71heptene (2).2) This achievement, as well as the ease of introducing suitable substituent into the bridgehead position of the bicyclo[l.l.O]butane skeleton, 31 led immediately to attempt to apply this method to the synthesis of some 1-bensothiepin derivatives.

Treatment of 2 with n-BuLi in THF at -6OOC 4' followed by quenching of the anion with methyl iodide gave l-methyl-4,5-benzo-3-thiatricyclo[4.1.0.02D7]heptene (3) in quantitative yield. Isomerization with [FUI(CO),C~]~ in chloroform at O°C for 10 min afforded a mixture of 3-methyl-(4) and 4-methyl-1-benzothiepin (5) in a combined yield of 98% [ratio 1 : 1.31. The separation of these isomers was rather tedious and proceeded by low temperature column chromatography on deactivated alumina containing 2.5% of water at -20°C (elution with pet. ether, bp <50°C).