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Pyrazolotropones from the cycloaddition of diazomethane to tropone

✍ Scribed by L.J. Luskus; K.N. Houk

Publisher
Elsevier Science
Year
1972
Tongue
French
Weight
198 KB
Volume
13
Category
Article
ISSN
0040-4039

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✦ Synopsis

The reactions of diazoalkanes with tropone have been reported to produce 2,4,6cyclooctatrienones as the only products.2 However, in the course of our studies of periselectivity in 1,3-dipolar cycloadditions to trienes,"' we have found that cyclooctatrienone is but one of many products formed upon reaction of diazomethane with tropone. In particular, 2,3-homotropone and pyrazolotropones are the major products of this reaction. Pyrazolotropones have been isolated previously from diazometnlne additions to troponoids,5 but our use of the Eu(dpm)o shift reagent has made possible : sofs of two pyrazolotropone structures for the first time. Tropone (10 mmoles) and diazomethane (from 14. mmole Diazald) were allowed to react at 0' in ether solution for 4 days. Thick layer chromatography gave products ,&-L_z in the approximate yields shown based on tropone.

2,4,6_Cyclooctatrienone, A, had spectral properties identical to those of an authentic sample prepared by the method of Cope.' The ir, nmr, and mass spectra of gwere the same as those reported for 2,3-homotroponev and differed significantly from those reported for 4,5-homotropone.e Although the molecular formula of X has been obtained from spectral data, the structure of 2 has not been determined.

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