The Regio- and Diastereoselectivity of the Intramolecular 2 + 2 Photocycloadditions of 4-(2'-Isopropyl-3'-butenyl)-2,5-cyclohexadien-1-ones

Article abstract of DOI:10.1021/jo00274a035

Irradiation (366 nm) of 4-carbomethoxy-4-(2'-isopropyl-3'-butenyl)-2,5-cyclohexadien-1-one (3) in pentane solution at -78 deg C gave the tricyclodecenone 4 rather than the alternative diastereomer, 5.The ability of the C(3) methoxy substituent to direct the regioselectivity of photocycloaddition to give the less stable diastereoisomeric series (cf. 5) was examined.However, irradiation of 7b (benzene, 25 deg C), in mixture with 8b, gave 9 rather than 11, while 8b gave the expected 10.The diastereoselectivity of reductive alkylation of methyl 2-methoxybenzoate with dl-4-iodo-3-isopropyl-1-butene to give 7a and 8a was determined to be 1.6:1.