TMSOTf generation

TMSOTf generation. Reactions th promoted by the combination of triflic bis(trimethylsilyl)urea]. 

TMSOTf generation. Reactions that require catalysis of TMSOTf can be promoted by the combination of triflic acid and bis(trimethylsilyl)acetamide [or bis(trimethylsilyl)urea]. 

The addition of dimethyl sulphide to a,/3-unsaturated carbonyl compounds in the presence of TMSOTf generates highly reactive 3-trialkylsilyloxyalk-2-enylenesulfonium salts, which permits the introduction of a wide variety of nucleophiles at the -position as well as a-functionalization. ... 

Other examples that involve intermediate allyl cations are illustrated in Scheme 1.4. The cationic palladium(II) complex [Pd(dppp)(PhCN)2](BF4)2 coordinates the carbonyl oxygen of benzaldehyde and the activated carbonyl carbon attacks the isoprene, forming the allyl cation 10 which then cyclizes to give the 4-methyl-6-phenyl-5,6-dihydro-2H-pyran [22]. 2-Oxopropyl acrylate 11, in the presence of trimethylsilyltrifluoromethane sulfonate (TMSOTf) and methoxytrimethylsilane (MeOSMT), generates the cation 11a which is an efficient dienophile that reacts easily with the cyclohexadiene to give the Diels-Alder adduct in good yield [23]. 

The addition of zinc organometallics to in situ generated oxenium ions by the reaction of mixed acetals with TMSOTf " allows a highly stereoselective preparation of protected a r/-l,3-diols of type 223 (Scheme 66). The addition of TMSOTf triggers also the allylic substitution of glycal derivatives, providing the substitution products of type 224 with excellent regio- and diastereoselectivity. 

Trimethylsilyl fluorosulphonate, generated by in situ reaction of fluorosulphonic acid with either tetramethylsilane or allyltrimethylsilane, has been proposed90 as a cheaper alternative to TMSOTf. 

With the realization that the efficiency and reproducibility in the conventional flask reaction is sensitive to the heat generated during syringe addition of the Lewis acid to the donor and acceptor, the reaction conditions of the sialylation using the N-acetylated donor was reinvestigated in pursuit of a practical route to a-sialylation. The initial optimization of the a-sialylation utilized the N-acetylated imidate 15 [27, 50, 51] and the galactose acceptor 6 in the presence of TMSOTf as an activator in... 

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