Eight β-allenic alcohols were synthesized and the tosylate and brosylate [3,5-dinitrobenzoate (Vie) in the case of 2-methyl-4,5-heptadien-2-ol] of each prepared. The rates of acetolysis (hydrolysis in the case of Vie) were determined titrimetrically. Solvolysis products were isolated and their structures assigned on the basis of spectra and properties. Each compound studied except Vie, exhibited a significant (assisted solvolytic rate) when compared to the saturated analog. The fact that Vie underwent hydrolysis only one-third as fast as 2-methyl-2-butyl 3,5-dinitrobenzoate is attributed to the rate-retarding inductive influence of the allene moiety. It was observed that 4,5-hexadien-2-yl tosylate (lb) rapidly rearranged during acetolysis, but all other substrates could be recovered unchanged after partial acetolysis. The fraction of cyclized or rearranged solvolysis products ranged from 0% for Vie to 100% for esters of 2,2-dimethyl-3,4-hexadienol (Va). The results are interpreted as evidence for homoallenic anchimeric assistance in the transition states for solvolysis; the intermediates have been formulated as bicyclobutonium ions except in the case of Vie. © 1969, American Chemical Society. All rights reserved.
