Sugars deoxyhalogeno

Reactions that have led to other deoxyhalogeno sugars do not necessarily lead to deoxyfluoro sugars, as, for example, in the attempted decomposition of fluoroformates, the treatment of diazoketones and of 2-deoxy-2-diazohexonates with hydrogen fluoride, and the reaction of benzoxonium ions with halide ions. The reaction2281229 by which fluoroformates are thermally or catalytically decarbonylated to give alkyl fluorides has been applied to carbohydrates. Both thermal and catalytic treatment of 6-0-(fluoroformyl)-l,2 3,4-di-0-isopropylidene-... 

In addition to the previous Chapter in this Series,1 two other reviews7,8 have since outlined the various methods for the preparation of deoxyhalogeno sugars. In the present Chapter, an attempt has been made to collate new information on the synthesis and chemistry of... 

Nucleophilic-displacement reactions constitute some of the earliest known methods for the preparation of deoxyhalogeno sugars. A variety of leaving groups have been used, including sulfonyloxy (usually jP-tolylsulfonyloxy or methylsulfonyloxy), halide, triphenyl-methoxy (trityloxy), acetoxy, phosphate, and nitrate. As Barnett has surveyed the reactions in Volume 22 of this Series,1 this subject will not be discussed comprehensively in the present Chapter instead, only some general comments will mainly be made that will also be relevant to later discussions. 

Other examples of the use of phosphorus-containing reagents for the synthesis of deoxyhalogeno sugars, by way of Arbusov-type reactions, are described in Section 11,5 (see p. 278). 

Deoxyhalogeno sugars are susceptible to nucleophilic attack, leading either to displacement, elimination, or anhydro-ring formation. The ease of displacement decreases in the order I > Br> Cl > F the iodo and bromo derivatives have, therefore, been especially utilized in such reactions, although several reactions with chlorodeoxy sugars have now been reported as a result of the increased availability of these compounds. The approach delineated in Section 11,1 (see p. 227) for predicting the reactivity of sulfonic esters can be expected also to be applicable, in an approximate and qualitative way,... 

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