Trichloroacetimidic esters

For tertiary alcohols, transition states corresponding to A and B are usually almost isoenergetic (for an exception see ref 40). Thus, thermolysis of the trichloroacetimidic ester of linalool affords a 60 40 mixture of the geranyl and neryl amides28. 

Ohler, E., and Kotzinger, S., Thermal reanangement of trichloroacetimidic esters of allylic a-hydroxyphosphonates. A convenient way to (3-amino-1-alkenylphosphonic acids, Synthesis, 497, 1993. 

Synthesh of amines by l3,3]sigmatropie rearrangement Trichloroacetimidic esters (2) of allylic alcohols (1) can be prepared in 80-100% yield (crude) by reaction with trichloroacetonitrile catal3rzed by the corresponding sodium or potassium alkoxide (O, ether). Inverse addition is preferred for secondary or tertiary alcohols. These esters undergo Claisen-type rearrangement at 25-140° to give allylic trichloroacetamides (3), in which the rrans-isomcr usually predominates. 

Liebigs Ann Chem 654 180 1962]. It is readily converted into its trichloroacetimidate esters by reaction with ally lie alcohols in CH2CI2, in the presence of DBU at to ambient temperatures [Anderson Overman J Am Chem Soc 125 12412 2003, Kirsch et al. Org Lett 9 911 2007] similarly prepared trichloroacetimidates of allylic alcohols were shown to undergo ether-directed Pd(II)-catalysed aza-Claisen rearrangements [Jamieson Sutherland Tetrahedron 63 2132 2007], and bis-trichloroacetimidates from 2-aminopropane-l,3-diols yielded dihydrooxazines through an acid catalysed cychsation [Rondot et al. Org Lett 9 247 2007],... 

In some cases, the mercury(II)- and palladium(II)-catalysed allylic Overman rearrangement of trichloroacetimidates can be accomplished under mild conditions at room temperature or even much lower temperature. For example, the trichloroacetimidic ester of geraniol 12 is converted to linalyl trichloroacetamide 13 when treated with 0.2 equiv of mercuric trifluoroacetate at room temperature for 10 min. This catalytic... 

Accordingly, phosphoric acid mono- and di-esters permit uncatalyzed glycosyl transfer from 0-(glycosyl)trichloroacetimidates (52a,55-57,58a,58b). The reaction is thus very useful in the synthesis of glycophos-pholipids (1,55), which are important constituents of cell membranes (1). Commonly, direct phosphorylation at the anomeric hydroxyl group leads to... 

Despite these restrictions, the acceptor-bound succinoyl MPEG28 was found to permit glycosylations with glycosyl trichloroacetimidates promoted by boron trifluoride, triflic anhydride, and trimethylsilyl or triethylsilyl triflates, with glycosyl halogenates promoted by silver triflate, and with thioglycosides promoted by the iodonium ion. It is compatible with long-term ester protection, with allylic,... 

Allyl imidate esters undergo [3,3] sigmatropic rearrangements to A -allyl amides. Trichloroacetimidates can be easily made from allylic alcohols by reaction with trichloroacetonitrile. The rearrangement then provides trichloroacetamides of iV-allyl-amines.176 177... 

The hydroxy ester (7.5 g, 56.8 mmol) was dissolved in cyclohexane/CH2Cl2 (2 1,100 mL) and cooled to 0 °C. Benzyl 2,2,2-trichloroacetimidate (10.6 mL, 56.8 mmol), followed by TfOH (0.75 mL, 8.5 mmol), was added. The soln was filtered, and the solid was rinsed with cyclohexane. The filtrate was washed with sat. NaHC03 and brine, and the organic layer was dried (Na2S04), and concentrated. The residue was distilled to afford the benzyloxy ester yield 10.3 g (80%) bp 160-165 °C/20Torr. 

After developing procedures for the activation and coupling of anomeric trichloroacetimidate and glycosyl phosphate donors as well as for the deprotection of acetyl and levulinoyl esters, we designed a synthesis utilizing all aspects of our automated chemistry. Trisaccharide 24, composed of three... 

Benzylation with benzyl trichloroacetimidate and a catalytic amount of triflic acid (TfOH) is a mild and efficient procedure (Scheme 2.1c).5 The acid protonates the nitrogen of the imidate moiety converting it into a very good leaving group. Nucleophilic attack by an alcohol introduces a benzyl ether. The procedure is often compatible with base- and acid-sensitive functionalities with esters, (7-isopropylidene and (7-benzylidene acetals. Benzyl trichloroacetimidate is commercially available but can easily be prepared by reaction of benzyl alcohol with trichloroacetonitrile in the presence of a mild base. 

Benzyl 2,2,2-trichloroacetimidate (bp 106-114 °C/0.07 kPa) alkylates alcohols in the presence of trifluoromethanesulfomc acid.311 Esters, imides, isopropylidene and benzylidene acetals are unaffected. This method allows the formation of benzyl ethers in molecules that are base-sensitive. In the example [Scheme 4,167],312 benzylation of the P-hydroxy ester 167.1.1 under the usual basic conditions would lead to retro-aldol reactions and/or elimination. A synthesis of the cellular messenger L-a-phosphatidyl-D-myo-inositol 3,4-bisphosphate exemplifies the use of trityl cation-promoted benzylation of two adjacent hydroxyls [Scheme 4.168].313314... 

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