Synthesis of Hexitols from Unsaturated Intermediates

Very little was published on the synthesis of hexitols from unsaturated intermediates between the time of Griner s work and 1933, when it occurred to me that it might be possible to add four hydroxyl groups to divinylglycol by means of a solution of silver chlorate containing a small amount of osmic acid. In carrying out this work I had the assistance of one of my students, Joseph Wiemann. We succeeded far beyond our expectations and obtained allitol, unknown up to that time, and d,l-mannitol. 

Another method of synthesis was also used. This involved the action of chloroacetaldehyde on the Grignard reagent derived from acetylene in order to obtain the meso divinylacetylene dichlorohydrin, CHsCl—CHOH—C=C—CHOH—CH,C1, from which one passed to the corresponding hexynetetrol, CHgOH—CHOH—C=C—CHOH— CHjOH. This, in turn, was reduced to the hexenetetrol, CH2OH— CHOH—CH===CH—CHOH—CHjOH, by means of Bourguel s catalyst, a dispersion of colloidal palladium on starch. When the hexenetetrol was hydroxylated by the use of silver chlorate and osmic acid, two hexitols, dulcitol and allitol, were obtained. 

It may be well to state at this point that the reagents used in any of the syntheses which follow are sufficiently mild to preclude the possibility of rearrangement of the hydrogen atoms on the carbon chain. Thus in the compounds which lead to allitol, those hydrogen atoms which are attached to secondary carbon atoms all lie on the same side of the carbon chain, just as they do in allitol. 

the precursors of allitol are the meso form of divinylglycol in the first of the above syntheses, and the meso form of the hexynetetrol and hexenetetrol in the second method of synthesis. 

It is to be noted that reduction of the acetylenic compound to the olefin with Bourguel s catalyst (palladium on starch) leads exclusively to the cis isomer. 

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II. Synthesis of Hexitols from Unsaturated Intermediates 1. Methods of Preparation... 

Very little work on the synthesis of pentitols had been carried out before 1928. Those pentitols which had been synthesized were made by the reduction of pentoses. Several pentitol intermediates had been synthesized" and it seemed desirable to attempt to complete the synthesis of pentitols from the unsaturated intermediates, using the methods which had been successfully employed in the synthesis of hexitols. 

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