Alditols sulfonylation

Replacement,a by Iodine, of Primary Sulfonyloxy Group(s) of a-, or a,u-0-Sulfonylated Alditols... 

Lithium chloride, preferably dissolved in absolute ethanol, has also been used306 419 420 for preparing alkyl chlorides. Dissolved in absolute ethanol-acetone (1 1, by vol.), it has recently414 found application with alditol sulfonates. Its action on l,4 3,6-dianhydro-2,5-di-0-mesyl-L-iditol, l,4 3,6-dianhydro-2,5-di-0-mesyl-D-mannitol, and l,4 3,6-dian-hydro-2,5-di-0-mesyl- (and -2,5-di-O-tosyl-) sorbitol resembles the action of sodium iodide on these compounds, i.e., the first displays no appreciable reaction, the second gives the 2,5-dichloro-2,5-dideoxy derivative, and the last two afford the respective monochloromonodeoxy-mono-O-sulfonyl derivatives. Treatment of l,4 3,6-dianhydro-2,5-di-0-mesyl-sorbitol during 48 hours at 180-90° gives some of a dianhydro-mono-chloromonodeoxy-sorbitoleen. 

Pyridine is widely used as a reaction medium in acylation and related reactions involving, for example, acyl chlorides, anhydrides, sulfonyl chlorides, or chlorosilanes, and has the particular advantage that it can function both as a catalyst and acid acceptor. It is usually the solvent of choice for the trimethylsilylation of alditols and sugars,292-298 and for various derivatization reactions such as tritylation and sulfonylation.299-307 The tritylation reaction has been reviewed.306... 

Similar findings have been reported with nucleosides and with acetals of alditols. It appears Aat sulfonylations of carbohydrates invariably result in preferential reaction at a primary hydroxyl group. 

A rather careful study of the competition between 0 -5, 0 -6, and 0 -3 participation in the reactions of a number of O-toluene-p-sulfonyl-alditols and -deoxyalditols has appeared. While the order of anchimeric assistance in the alkaline hydrolysis of cu-chloro alcohols is O -3 > 0 -5 > 0"-6, Hartman and Barker (second reference in Ref. 108) found the order primary 0 -5 > secondary 0 -5 = secondary 0 -3 > primary 0 -6 from their studies of primary O-toluene-p-sulfonyldeoxyalditol displacements. Thus, alkaline treatment of (206) yields (207) directly and not via the epoxide (208), since epoxide (209) yielded only glycol and none of the tetra-... 

---