Benzoxonium salts

In the case of D-glucose-derived hydroxyglycal ester 8, low temperature chlorination affords an approximate 1 8-mixture of the cw-dichloride of a-D-waHHo-configuration (10) and the a-D-g/wco-benzoxonium salt (11), of... 

In the following discussion, the dioxolanylium (2) and dioxanylium ring-systems will be referred to simply as acyloxonium derivatives, as the carboxonium ion of the ring is formally derived from a carboxylic acid. Thus, system 2 is an acetoxonium salt when R = Me, and a benzoxonium salt when R = Ph. 

Penta-0-benzoyl-/3-D-glucopyranose or, better, tetra-O-benzoyl-a-D-glucopyranosyl chloride in carbon tetrachloride can be converted at 75° with antimony pentachloride into a mixture of benzoxonium salts that contains 38% of the D-gluco, 25% of the D-manno, 10% of the D-altro, and 20% of the D-ido derivatives these results indicate... 

The mixture of benzoxonium salts is subject, in various solvent media, to an equilibration reaction similar to that involving the acetoxonium salts 59 and 62. The equilibrium proportions of the four benzoxonium ions (see Table II) correspond approximately to those found for the four acetoxonium ions 59, 60, 61, and 62. The content of the n-gluco ion is somewhat greater, and that of the D-ido ion is proportionately lower, but, evidently, a change in the nature of the acyl group does not lead to substantial alteration in the equilibrium composition. 

Acetals formed from ketones and 1,2-diols are of major significance in carbohydrate chemistry, and can be converted into acylox-onium salts only in special cases. Acetals (7) from acetophenone react with the highly reactive ketonium salts (8) to give benzoxonium... 

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