The outcome of the photocycloaddition of cyclohex-2-enones to 2-alkylprop-2-enenitriles differs basically from that of the corresponding 2-alkylbut-1-en-3-ynes. While the latter afford mainly products resulting from 1,6-cyclization of the intermediate triplet alkyl-(prop-2-ynyl) 1,4-biradical, the former give only cyclobutane-carbonitriles resulting from 1,4-cyclization of the singlet alkyl-cyanoalkyl 1,4-biradical.
The outcome of the photocycloaddition of cyclohex-2-enones to 2-alkylprop-2-enenitriles differs basically from that of the corresponding 2-alkylbut-1-en-3-ynes. While the latter afford mainly products resulting from 1,6-cyclization of the intermediate triplet alkyl-(prop-2-ynyl) 1,4-biradical, the former give only cyclobutane-carbonitriles resulting from 1,4-cyclization of the singlet alkyl-cyanoalkyl 1,4-biradical.