Synthesis and Solvolysis of syn- and anti-(6-Oxabicyclohex-3-yl)methyl p-Bromobenzenesulfonates

Article abstract of DOI:10.1021/jo00330a027

syn- and anti-3-(Hydroxymethyl)-6-oxabicyclo<3.1.0>hexanes (3a and 4a) have been prepared and the solvolysis rates of their p-bromobenzenesulfonate esters have been determined in aqueous ethanol.The solvolysis rate of 3c was found to be ca. 1E4-1E5 times faster than the rate of its anti epimer 4c but, unexpectedly, of similar order to the solvolysis rate of 6c.Both 3c and 6c yielded the same mixture of products, 6a and 6b, exclusively.The α- and β-deuterium isotope effects on the solvolysis of 5c and 3c-3-d were 1.034 and 1.084 per deuterium atom, respectively.Solvoly sis of 6c-6-d showed an α-isotope effect of 1.086.Also, it yielded a mixture of exo-substitution products with an equal distribution of the deuterium atom at C1 and C6.On the basis of these experimental data, solvolysis of 3c and 6c must have proceeded by way of the common oxonium ion intermediate (7) which arises from participation of the nonbonded electrons on the oxygen atom.The solvolysis rate of 4c is of similar magnitude to those of 1c and 2c; solvolysis yielded 80percent substitution products and thus was interpreted to proceed via a solvent-assisted ionization pathway.