NEW RESULTS OF SULFUR CHEMISTRY OF 1,6-METHANO[10] ANNULENE AND 1H-CYCLOPROPABENZENE

Abstract

Abstract Literature data about the stereochemistry of electrophilic attack on 1,6 - methano[10] -annulene (1) appear to be conflicting. In an earlier report on the protonation of 1, the π-electron density was assumed to be greater on the endo side of the annulene ring. In order to see how decisive is the steric factor, we tried to obtain an adduct of 1 with bulky electrophile. Thiocyanogen (SCN)2, was chosen as reaction partner, not only for its large steric requirements, but also for its low electrophilicity. The reagent could thus be expected to discriminate between the exo and the endo region, if an unequally distributed electron density, and not the steric hindrance of the bridge, controls the stereochemistry. At the same time thiocyanogen was used hoping to obtain a stable addition product, displaying only a low re-aromatization tendency (by HNCS elimination), since - SCN is a relatively poor leaving group.