Propellanes .100. The Nature Of The Stereoelectronic Effect In The Highly Stereospecific Hydroxyl Elimination From Syn,Anti-[4.3.3]Propellane-8,11-Diol Upon Isobutane Chemical Ionization

A stereospecific 18O-labelling study shows that the syn-hydroxy group is preferentially lost from the syn, anti-title diol upon i-C4H10 chemical ionization, indicating occurrence of a stereoelectronic effect in this process. A collision-induced dissociation study of deuterium- and 18O-labelled analogs shows that a symmetrical ether structure is not formed in the above process by an SNi mechanism. This result leads to the conclusion that the stereoelectronic assistance of the anti-OH group in the loss of the syn-hydroxyl is expressed either in a weak transition state interaction or by other processes such as β-elimination via hydrogen transfer with concomitant double bond formation.