Abstract
Cycloheptatriene analogues are known to react with 4-phenyl-1,2,4-triazole-3,5-dione (PTAD) as there two tautomeric forms; cycloheptatriene and norcaradiene. In addition to those [4+2] additions, [2+2], [6+2], and ene additions are known to occurred. In this study, the reaction of a 7,7-dimethylcycloheptatriene having a chiral alcohol moiety at the 3-position and PTAD was found to be highly regio- and stereoselective to result in [4+2] addition at the cycloheptatriene tautomer. The nmr measurement at -78 °C disclosed that the primarily product is not that adduct, but a [2+2] adduct at the 3,4-position. The stereoselectivities for the formation of the both adducts depend on the solvent and the existence of the hydroxy group at the chiral alcohol moiety. In contrast, tetracyanoethylene of a weaker dienophile reacts at the norcaradiene tautomer. The stereoselectively of the addition is not high, but shows characteristic change by the solvent used. The result with other dienophile are also presented.
