Transoid Homoallylic Proton-Proton Coupling Constants

Abstract

Transoid homoallylic coupling constants (5J_H,H) for six compounds (5,10-dihydroindeno[2,1-alindene and confertifolin derivatives) of fixed stereochemistry were determined and compared with calculated values. Magnetic equivalence limited discrete determination of ⁵J_trans and ⁵J_cis to three of these compounds. The single compound where unequivocal assignment could be made revealed ⁵Jtrans > ⁵J_cis; this was supported in two other compounds by tentative assignment. Changes in the magnitude of the couplings suggested that substantial substituent effects may be operative. INDO-MO calculations correctly predicted the angular dependence but incorrectly predicted ⁵J_cis > ⁵J_trans.