ISSN:
0018-019X
Schlagwort(e):
Chemistry
;
Organic Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
The photolysis and thermolysis of the Cyclopropyl silyl ketones 3, 4, and 5 are described. On n,π* excitation, the silyl ketones 3 and 4 undergo a Norrish-type-II reaction involving γ-H abstraction, cyclopropyl ring cleavage followed by retro-enolization to the acylsilanes 6 and (E/Z)-12, respectively. As a common product of 3 and 4, the dihydrofuran 7 is formed via the alternative C(α)-C(β) cleavage of the cyclopropyl moiety. Compounds 6, 7, and (E/Z)-12 are new types of acylsilane photoproducts. The irradiation of acylsilane 5 gave the analogous dihydrofuran 15 as the only product. On photolysis of 3 and 4, products 8A + B and 13A + B, derived from a siloxy carbene intermediate, were found as well. On thermolysis of 3 and 4, the acylsilanes 6 (80%), and (E)-12 (33%) and (Z)-12 (34%), respectively, are formed as the only products. Their formation may occur via a [1, 5] sigmatropic H-shift. The thermolysis of 5 gave the diene 16 whose formation can be explained by insertion of a siloxycarbene into the neighboring cyclopropane leading to the cyclobutene 28 as thermally unstable intermediate.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/hlca.19900730420
