Some Transformations of 1,6,7,7-Tetrachlorobicyclo[4.1.0]heptan-3-one. Crystal and Molecular Structure of 4-(Dichloromethylene)-1-methyl-5,6-dihydro-1h-indazol-7(4H)-one

Abstract

Treatment of the title tetrachloro ketone with triethylamine generates 6,7,7-trichlorobicyclo-[4.1.0]hept-1(2)-en-3-one (4), which can be trapped by furan to give two cycloadducts. In the absence of trapping agent, compound (4) undergoes a methylenecyclopropane rearrangement to yield 5-chloro-6-( dichloromethylene ) bicyclo [3.1.0]hexan-2-one. The strained enone (4) can also be intercepted by diazomethane, which affords the title indazolone, whose characterization was supported by a single-crystal X-ray study.