2-Fluoro-l-methylpyridinium

Abbreviations IMP, 2,4,6-trimethylpyridinium fluoride FMPTs, 2-fluoro-l-methylpyridinium tosylate Ishikawa, Ishikawa reagent (Ref. 74) Mitsunobu, through Mitsunobu reaction (Ref. 80) NBS, A-bromosuccinimide Piv, pivaloyl and Py, pyridine. 

There are also useful procedures for preparation of azides directly from alcohols. Reaction of alcohols with 2-fluoro-l-methylpyridinium iodide followed by reaction with lithium azide gives good yields of alkyl azides.75... 

In an early example, Mukaiyama and coworkers used hetaryl onium salts for nucleoside synthesis. The active hetaryl onium salt is generated in situ from the reaction of 2-chloro-3-ethylbenzoxazolium tetrafluoroborate 77 and the glycosyl acceptor. With benzimidazole as glycosyl acceptor, the resulting 2-(l-benzimida-zoyl)benzoxazolium tetrafluoroborate 78 was obtained. The reaction between the hetaryl onium salt 78 and hemiacetal donor 1 occurs at 60 °C to activate the hemiacetal and thereby reveal the glycosyl acceptor. This procedure led to the formation of nucleoside 80 with exclusive 1,2-trans selectivity [139]. The nucleoside 81 was similarly prepared. Alternatively, 2-fluoro-l-methylpyridinium tosylate 79 directly... 

Fluoro-l-methylpyridinium p-toluenesulfonate (2) is a stable crystalline solid which is synthesized from the readily available 2-fluoropyridine (1) and methyl p-toluenesulfonatc. 

Several methods have been reported for the preparation of glycosyl fluorides7 but the most common procedure is treatment of a thioglycoside with NBS (iV-bromosuccinimide) and (diethylamino)sulfur trifluoride (DAST)8 or the reaction of a lactol with DAST or 2-fluoro-l-methylpyridinium p-toluenesulfohate.7 9 An alternative and interesting method is the treatment of a 1,2-anhydro-pyranoside with tetra-n-butylammonium fluoride (TBAF). 

The most commonly used biopolymers, such as agarose, contain alcoholic hydroxyl groups which can be activated with cyanogen bromide however, better methods have recently been developed including activation with sulfonyl chlorides (17), 2-fluoro-l-methylpyridinium toluene sulfonate (FMP) (10), and chlorocarbonates (18). The first two are commercially available as activated supports tresyl-activated Sepharose (Pharmacia) and FMP-Trisacryl (BioProbe International). The newer methods yield more stable bonds, which preclude leaching of the enzyme from the matrix. Most of these activated supports are too expensive for commercial use in a large process bioreactor however, they may be extremely useful for preparing analytical bioreactors. 

Primofy amines. A new method for preparation of primary amines involves N-alkylation of this derivative of hydroxylamine, dehydration of the product, 2, to 4, and finally acid hydrolysis of the N-benzylidenealkylamine (4) to the amine 5. HMPT is the solvent of choice for the alkylation step. 2-Fluoro-l-methylpyridinium p-toluenesulfonate (3) is superior to tosyl chloride for the second step. 

Mukaiyama and coworkers reported that totally benzylated ribofuranose smoothly reacted with 2-fluoro-l-methylpyridinium tosylate in the presence of triethylamine at room temperature to afford an anomeric mixture of the corresponding ribofuranosyl fluorides in high yield (O Scheme 4) [37]. 

MeCHO vii, 2-fluoro-l-methylpyridinium toluene-p-sulphonate, Et N viii, LiOH... 

In a recent example of p-lactam formation dehydration ofphenoxyacetic acid with 2-fluoro-l-methylpyridinium p-toluenesulfbnate in the presence of diaryhmines is proposed to proceed thorough the pyridinium intermediate 142 which leads to phenoxyketene, which reacts by [2 + 2] cycloaddition with the imine forming the product ds-P-lactam (Eqn (4.87)). Similahly propylphosphonic anhydride (T3P) was also successful in carboxylic acid activation (Eqn (4.88)). 

A mixture of 2-hydroxypropiophenone and triethylamine added with stirring at room temp, under argon to a suspension of 2-fluoro-l-methylpyridinium tosylate in methylene chloride, after 1 hr. stirring an aq. soln. of Na-dithionite added, and stirring continued 2 hrs. until the mixture becomes yellow propiophenone. Y 81%. F. e. s. M. Wada, M. Imaoka, and T. Mukaiyama, Chem. Lett. 1976, 381. 

A novel method for the preparation of primary alkylamines from alkyl halides involves the use of AT-benzylhydroxylamine. iV-Alkylation followed by treatment with 2-fluoro-l-methylpyridinium toluene-/ -sulphonate yields the imine... 

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