Abstract
In view of the successful resolution of methylethyl-iso-butylmethanol by Doering and Zeiss and the revival of interest in the optical resolution of tertiary alcohols, it seemed feasible that an attempt to resolve a tertiary acetylenic alcohol might throw some light both on the reaction of the alcohol with phthalic anhydride in the presence of a tertiary base and the behaviour of an alkaloidal salt of the hydrogen phthalic ester in solution. It was particularly convenient that two such alcohols - 3-tftethylpent-1-yn-3-ol and 3:5-dimethylhex-1-yn-3-ol - were available commercially: it was, in addition, fortunate that the latter happened to be the acetylenic analogue of methylethyl-iso-butylmethanol which had been the subject of the work by Doering and Zeiss. Hence, if the unsaturated alcohol could be resolved and then reduced to the fully saturated compound, it would confirm the original resolution and provide an interesting comparison. In actual fact, both 3-naethylpent-l-yn-3-ol and 3:5-dimethylhex-1-yn-3-ol have been readily converted into crystalline hydrogen phthalic esters by the method outlined above and they have both been resolved into their optical antipodes by means of fractional crystallisation of the brucine salts of their hydrogen phthalic esters. The active alcohols have been reduced catalytically by hydrogen to the corresponding saturated alcohols 3-methylpentan-3-ol and 3:5-dimethylhexan-3-ol (methyldiethyl-methanol and methylethyl-iso-butylmethanol respectively). The first of these, as was to be expected, was found to be devoid of optical activity; the second had an optical activity almost identical with that reported by Doering and Zeiss. Determinations of the rotatory powers of (+)-3:5-dimethylhex-1-yn-3-yl hydrogen phthalate in a number of solvents produced sane interesting comparisons of the effect of different solvents and solvent groups and provided some information on the optical rotatory dispersion of this compound.