Zemplen-Helferich modification

In the early works, Hg salts were often used in place of the Ag salts to initiate the reaction. This has been called the Zemplen-Helferich modification. 

In the Koenigs-Knorr method and in the Helferich or Zemplen modifications thereof, a glycosyl halide (bromide or chloride iodides can be produced in situ by the addition of tetraalkylammonium iodide) is allowed to react with a hydrox-ylic compound in the presence of a heavy-metal promoter such as silver oxide, carbonate, perchlorate, or mercuric bromide and/or oxide,19-21 or by silver triflu-oromethanesulfonate22 (AgOTf). Related to this is the use of glycosyl fluoride donors,23 which normally are prepared from thioglycosides.24... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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