Conformation et reactivite de derives [4.n.0] bicycliques a fonction trans—XXII : Influence d'un méthyl en position β sur les vitesses relatives des réactions d'élimination syn et anti dans la série bicyclo [4.2.0] octanique trans

Rate constants and reaction products, in different base-solvent systems, are reported for 4e-methyl 3e-tosyloxy trans bicyclo 4.2.0] octane 4 and 4a-methyl 3e-tosyloxy trans bicyclo 4.2.0] octane 5. These results are compared with these relating to the parent compound 6. The axial β-methyl increases reactivity and favours elimination with respect to competitive substitution, and equatorial β-methyl has the opposite effect. The relative reactivities of diequatorial and syn axial-equatorial eliminations determined from 4 and 5 depend mainly on the influence of the substituent. These compounds are not suitable for determining the real difference of reactivity between the two elimination process. The origin of the methyl group influence, and a scheme of the reactions which account for this behaviour, are discussed.