K. Takeda et al., DIELS-ALDER REACTION OF ALPHA-SUBSTITUTED ACRYLATES AND ALPHA-(METHYLENE)LACTONES - CONFORMATION OF DIENOPHILES AND ENDO EXO SELECTIVITY/, Tetrahedron, 50(37), 1994, pp. 10839-10848
Diels-Alder reaction of 1,6-bis(trimethylsilyloxy)-2,4-hexadiene with
alpha-substituted acrylates and 5 to 7- and 9 to 11-membered alpha-(me
thylene)lactones has been carried out to examine correlation of dienop
hile structure with endo/exo selectivity. While the conformationally f
lexible acrylates produced cycloadducts of endo/exo = 59:41 to 74:26,
the 5 to 7-membered lactones with rigid s-cis conjugated system provid
ed cycloadducts of endo/exo = 13:87 to 32:68 and the 9 to 11-membered
lactones which can take both s-cis and s-trans conformation afforded e
ndo/exo ratios of 37:63 to 57:43.