Rotational isomerism in fluorene derivatives. XX. Conformational equilibria of 9-substituted 9-(o-methylthiomethylphenyl)- and 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes

Abstract

Several 9-substituted 9-(o-methylthiomethylphenyl)fluorenes and their oxidation products, 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes, were prepared. Each equilibrium constant at room temperature or at low temperature was investigated and the conformational equilibria [Formula: see text] of these compounds are discussed by comparing them with those of the corresponding 9-substituted 9-(o-methylthiophenyl)fluorenes and 9-substituted 9-(o-methylsulfinylphenyl)fluorenes in which the o-substituents were one CH2 unit shorter than those of the title compounds. Kinetic data for the internal rotation of several compounds are also given. Key words: conformational isomerism, restricted rotation, 9-arylfluorenes.