Trichloroacetimidate

Trichloroacetonitrile reacts with glycosidic hydroxy groups of protected sugars to form glycosyl trichloroacetimidates (R. R. Schmidt, 1980, 1984,1985,1986 B. Wegmann, 1988). The imidate is substituted by alcohols in the presence of trimethylsilyl trifluoromethanesulfonate... 

Schlosser s super base 615 f. Schmidt trichloroacetimidate glyco-sidation 528,531,537,556 Schwartz s reagent 606, 616 scopadulcic acid A 571 scopadulcic acid diterpenes 569 secocorrin 100, 122, 126 f., 130... 

Glycosyl trichloroacetimidate donors in the presence of selenoglycoside acceptors can be used with triethylsilyl triflate as promoter. 

A related planar chiral Co-based oxazoline palladacycle COP-X (46) was later found to be of higher synthetic utility as it permitted the use of benzimidates, [62] as well as allylic trifluoro- [63] and trichloroacetimidates [64, 65]. 46 was found to be superior to its ferrocene analogue 41 [61] in a number of aspects such as ease of... 

Nomura H, Richards CJ (2007) An investigation into the allylic imidate rearrangement of trichloroacetimidates catalyzed by cobalt oxazoline palladacycles. Chem Eur J 13 10216-10224... 

Benzyl groups are usually introduced by the Williamson reaction (Section 3.2.3). They can also be prepared under nonbasic conditions if necessary. Benzyl alcohols are converted to trichloroacetimidates by reaction with trichloroacetonitrile. These then react with an alcohol to transfer the benzyl group.183... 

Cyclization of. V-alkeny lam ides to 2-oxazolines was achieved in very mild conditions with fert-butyl hypoiodite <06OL3335>. The 5-exo-dig gold(I)-catalyzed cyclization of propargylic trichloroacetimidates 129 proceeded with remarkably efficiency under very mild conditions to give 4-methylene-4,5-dihydrooxazoles 130 in good yields. The mildness of the protocol was clearly responsible for the lack of isomerization of the final products to the corresponding, thermodynamically more stable, oxazoles <06OL3537>. 

These results encouraged the authors to attempt the synthesis of more-complex oligosaccharides, such as the Lex and Lea derivatives, 65 and 66, respectively. After formation of the (1 — 3)-fucosyl linkage, as promoted by HC104-Si02, in a stereo-and regio-selective manner, the peracetylated galactosyl trichloroacetimidate was added to afford the desired Lex derivative 65 in 62% yield. The same method was applied to obtain the Lea derivative 66 in 59% (Scheme 14).86... 

The on-column synthesis approach was also explored, followed by in situ purification of the products for the glycosylation reactions using trichloroacetimidates. The authors primed the top of a standard silica chromatography column with perchloric acid immobilized on silica. After charging both reactants, dissolved in dry CH2C12, onto the... 

SCHEME 15. Synthesis of an Avermectin B1 analogue by glycosidation of a trichloroacetimidate donor catalyzed by HC104-Si02. 

Trisaccharide 80 was synthesized by a similar approach, in which a rhamnoside was formed in 86% yield, transformed into its trichloroacetimidate, submitted to the second glycosylation step promoted by H2S04-silica (84% yield), and subsequently deprotected to 80.91... 

Trichloroacetimidate-based glycosylation promoted by perchloric acid-sibca, J. Org. Chem., 70(22), (2005) 9059-9062. 

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