PHOTO-CHEMICAL REACTIONS OF 6-BETA,GAMMA-CYCLOPROPYL KETONES DERIVED FROM BICYCLO[4.2.1]NONA-2,4,7-TRIEN-9-ONE

Simmons-Smith reaction of trienone 4 and its ketal 7 led to the cyclopropyl ketones 5, 6, 10, and 11; reduction provides 14-17. The homologous ketone 21 is similarly prepared from 23. Photolysis of reduced ketones 15 and 16 leads to mixtures of monocyclic olefins through decarbonylation and opening of the cyclopropane rings, and these reactions are rationalized by stepwise biradical pathways. Irradiation of 6 furnishes only the tetrahydronaphthalene 43, which is considered to result from thermal cyclization of the cyclodecatetraene 42. Both 5 and 10 undergo decarbonylation with formation of bicyclo[6.1.0]nonatriene 44. The apparent photostability of 11 is rationalized as the result of a rapid, degenerate 1, 3-acyl shift interconverting the enantiomers 11a and 11b. © 1979, American Chemical Society. All rights reserved.