PHOTOCYCLOADDITION OF 2-CYANOCYCLOALK-2-ENONES TO 2,3-DIMETHYLBUT-2-ENE

Irradiation of 5,5-dimethyl-6-oxocyclohex-1-ene-1-carbonitrile (1) in the presence of 2,3-dimethylbut-2-ene afforded -3,4,4a,5,6,7-hexahydro indeno[1,7-c,d]-1,2-oxazole (3) in nearly quantitative yield. In contr ast, 4,4-dimethyl-5-oxo-cyclopent-1-ene-1-carbonitrile (2) under the s ame conditions reacted not to a tricyclic isoxazole but to a 2:1 mixtu re of amethyl-2-oxo-bicyclo[3.2.0]heptane-1-carbonitrile (4) and -dime thylbut-3-en-2-yl)cyclopentane-1-carbonitrile (5), respectively.