Thermal conversion of phorone into isophorone via (trimethylsilyl)oxyhexatriene (soh) cyclization
✍ Scribed by Daniel S. Torok; William J. Scott
- Book ID
- 104225795
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- French
- Weight
- 287 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0040-4039
No coin nor oath required. For personal study only.
✦ Synopsis
Heating of 3-Z-4-(trimethylsilyl)oxy-2,6-dimethylhep~a-l,3,5-~iene, readily available from phorone (LDA; TMSCI), at 220 OC caused isomerization and cyclization to afford isophorone after deprotection.
The development of methods for the synthesis of cyclohexenones remains one of the most important endeavors of the synthetic organic chemist. 3-5 Based on earlier findings of Scati and Yoshikoshi,7 Magnus proposed a general approach to the annulation of cyclohexenones involving the thermal conversion of enolates derived from acyclic dienones.
It was not until recently that we9 and FehrlO were able to demonstrate the viability of Magnus' proposal. We reported9 that at 110 OC the all-cisll enolate of a fully conjugated dienone undergoes a hexatriene-like cyclizationl2 at a very slow rate. The silyl enol ether is also resistant to cyclization at 110 oC.9 The electronic bias against thermal cyclization of these electron-rich hexatrienes could