Photochemical reactions. 139th Communication. Photochemistry of acylsilanes: 1. Siloxcarbene formation versus γ-H-abstraction
✍ Scribed by Markus E. Scheller; Bruno Frei
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 975 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The Syntheses and the photolyses of the acylsilane 1 and the corresponding methyl ketone 2 are described. On n,π*‐excitation, the silyl ketone 1 as well as the methyl ketone 2 undergo a Norrish type II reaction involving γ‐H‐abstraction and fragmentation to the diene 12, and acetone (20) or the acylsilane 26, respectively. The methyl ketone 2, but not the acylsilane 1, isomerizes to cyclobutanols (21A‐D). Additionally, compound 1 shows photochemical behavior typical of acylsilanes undergoing rearrangement to the siloxycarbene intermediate c. Insertion of c into the OH‐ond of the enol 28 leads to compound 13. Initial trapping of the siloxycarbene c by H~2~O, however, gives rise to the formation of compounds 16–18. As minor photolysis products of 1, compounds 14 and (Z)‐15 were formed; however, on vapor phase thermolysis (520°) of 1, compounds 14 and (E/Z)‐15 were obtained in 92% combined yield. To a small extent the acylsilane 1 also undergoes Norrish type I cleavage leading to the acid 19.