作者:Paul Müller、Hassan Imogai
DOI:10.1002/(sici)1522-2675(19990310)82:3<315::aid-hlca315>3.0.co;2-t
日期:1999.3.10
The optically active cyclopropanecarbonyl azide 6 (ee 90%) was synthesized from the known cyclopropanecarboxylate 4. Upon heating in refluxing benzene, 6 rearranged to the dihydroazepinone 9 (ee 65%) via the isocyanate 7 and the enamide 8. In contrast, the dimethyl-substituted cyclopropanecarbonyl azide 20 rearranged to the isocyanate 21, but decomposed at higher temperatures rather than to undergo Cope rearrangement to 22. The results are consistent with a mechanism involving a boat-like endo-transition state 11 for the rearrangement, which may nor be reached with the dimethyl derivative 21 for steric reasons. The origin of change in enantiomer composition, upon going from 6 to 9, is at present unknown.