Title: Reactivities of Stable Rotamers. X. Reactions of 9-(2-Formyl-1-naphthyl)fluorene Rotamers and Related Compounds
Abstract: Rotational barrier (ap→sp) in 9-(2-formyl-1-naphthyl)fluorene was determined: ΔH\eweq24.0 kcal/mol and ΔS\eweq−7.9 e.u. Oxidation of the aldehyde with chromium(VI) oxide was extremely slow in the ap form, whereas it proceeded smoothly in the sp form. As models of the 2 steps involved in the aldehyde oxidation, oxime formation of the aldehyde and oxidation of related alcohols were carried out to conclude that the second elimination step in the aldehyde oxidation is slow in the ap form because of the steric effect. Dehydration of the oxime of the aldehyde exhibited a large ksp/kap value as well. Sodium tetrahydridoborate reduction and Grignard additions of the aldehyde were also carried out to show that the former gave a large ksp/kap value whereas the latter exhibited rather a small ksp/kap. The implication of the results is discussed.