DIMETHYLDIOXIRANE CONVERTS BENZENE OXIDE OXEPIN INTO (Z,Z)-MUCONALDEHYDE AND SYM-OXEPIN OXIDE - MODELING THE METABOLISM OF BENZENE AND ITS PHOTOOXIDATIVE DEGRADATION/

Oxidation of 7-oxabicyclo[4.1.0]hepta-2,4-diene (benzene oxide)/oxepin with dimethyldioxirane (DMDO) gave mainly (Z,Z)-muconaldehyde, with c omplete diastereoselectivity. Similarly, 2-methyl-7-oxabicyclo[4.1.0]h epta-2,4-diene (toluene 1,2-epoxide)/2-methyloxepin gave (Z,Z)-1,6-dio xohepta-2,4-diene, while 2,6-dimethyl-7-oxabicyclo[4.1.0]hepta-2,4-die ne (1,2-dimethylbenzene 1,2-epoxide)/2,7-dimethyloxepin gave (Z,Z)-2,7 -dioxo-3,5-octadiene. By monitoring the DMDO oxidation of benzene oxid e/oxepin by H-1 NMR spectroscopy, a significant byproduct was identifi ed as 4,8-dioxabicyclo[5,1.0]octa-2,5-diene (sym-oxepin oxide). This o bservation supports the hypothesis that the route to (Z,Z)-muconaldehy de proceeds from oxepin via 6,8-dioxabicyclo[5.1.0]octa-2,4-diene (oxe pin 2,3-oxide), with a minor pathway leading to sym-oxepin oxide. The DMDO oxidations described provide model systems for the cytochrome P45 0-dependent metabolism of benzene and for the atmospheric photooxidati on of benzenoid hydrocarbons.