Silver salts, with trimethylsilyl

In an analogous reaction, 1-trimethylsilyl-l-alkynes have been synthesized in good to excellent yield on treatment with trimethylsilyl chloride, catalytic amounts of silver salts, and DBU in refluxing dichloromethane (Scheme 1.61).135... 

Pale and coworkers provided the first example of combined desilylation/coupling catalytic for silver. They found that 1-trimethylsilyl-l-alkynes in the presence of tetrakis(triphenylphosphine)palladium, a silver(I) salt, and an activator (potassium carbonate in methanol, or TBAF-3H20) in DMF coupled with vinyl triflates and aryl iodides to give enynes good yields (Scheme 1.66).143,144 Although silver salt was not necessary for reaction when TBAF-3H20 was used for activation of the carbon-silicon bond, a small to significant improvement was observed for all reported... 

Other reactive halides employed include butyl iodide to yield butyl esters with, for example, the silver salts of methane- and ethanesulphonic acids106 or p-nitrobenzyl chloride or bromide, reacting in pyridine solution with sulphonates to yield addition product with pyridine molecules107. Classifiable here also is conversion to trimethylsilyl derivatives with bis (trimethylsilyl) trifluoroacetamide108. 

Conversion of the resulting separate D-seco D-E trans i-vincadiffor-mine diols 198-201 to their primary tosylates and tertiary trimethylsilyl-oxy derivatives 202-205 and coupling to vindoline by the chlorination-silver tetrafluoroborate-potassium borohydride sequence provided amino tosylates 206-209, which could be directly subjected to cyclization or, alternatively, converted to the C-20 -C-21 epoxides 178, 181, 210, and 211 by reaction with tetrabutylammonium fluoride (Scheme 53). While cyclization of the tosylates 206-209 led essentially only to quaternary salts which could be debenzylated to provide the lower energy atropi-somer of vinblastine (1), leurosidine (56), vincovaline (184), and its C-20 epimer (212) respectively, cyclization of the epoxides 178, 181, 210, and... 

The electrophilic addition of arylbis(arylthio)sulfonium salts to glycals in the presence of alcohols, directly provide 2-thio-(5-glycosides with good stereoselectivity [162]. Stereoselective syntheses of [5-glycosides were also obtained from the reaction of 1,2-trans acetoxysele-nides, prepared by treatment of glycals with phenylselenyl chloride and silver acetate, in the presence of trimethylsilyl triflate [163]. Combined application of this method and the trichlo-roacetimidate method (see section 3.3) was suggested for the synthesis of functionalized precursors of the olivomycin C-D-E trisaccharide [164] (Scheme 34). 

Formation and Reaction of the Trimethylsilyl Ester of Squaric Acid. The most common method employed in the synthesis of squarate esters uses expensive silver nitrate and goes through the explosive disilver salt of squaric acid. It was conceived that sUyl esters of squaric acid 38 may be considered as silyl enol ethers that can undergo Si-O cleavage in the presence of a suitable fluoride source and that O-alkylation may be affected using electrophilic halides. Upon preparation of thebis(trimethyl-silyl) squarate 39 using BSA and reaction in situ with p-methylbenzyl bromide in the presence of a fluoride source, the desired benzyl squarate 40 was obtained in about 50% overall yield (eq 42). ... 

---