Photochemistry of (o-Methylphenyl)alkadienes: Attempted Intramolecular Trapping of the Resulting o-Xylylenes

Article abstract of DOI:10.1021/jo00149a018

The photochemistry of a series of o-methylphenyl dienes was investigated in order to determine if the resulting o-xylylenes could be trapped in an intramolecular Diels Alder reaction in synthetically useful yields.Irradiation of 3 gave meta-isomer 4 as the major product along with lower yields of double bond migration product 5 and the desired cycloadduct 6.The best yield of 6 (24percent) was obtained by irradiation of 3 with a low-pressure mercury vapor lamp at low temperatures.The other compounds investigated gave none of the intramolecular Diels-Alder product of the o-xylylene.Irradiation of 17 gave only double bond migration product 18.Irradiation of 22 gave an excellent yield of (2+2) cycloadduct 23.Irradiation of 26 gave meta-isomer 28, double bond migration product 27, and 29, a (2+2) cycloadduct of 28.