2- Chloro-l-methylpyridinium iodide

CMPI, DABCO.cljoxane, 2 h, 20°, 96% yield. co H (CMPI = 2-chloro-l-methylpyridinium iodide)... 

Chloro-l-methylpyridinium iodide [ 14338-32-0] M 255.5, m 203-205°, 205-206°(dec), 207°. Purified by dissolving in EtOH and adding dry Et20. The solid is washed with Me2CO and dried at... 

Levulinic esters. Levulinic esters of sugars can also be prepared by Mukaiyama s method for esterification with 2-chloro-l-methylpyridinium iodide (8, 95-96). Deblocking of the ester group is possible with hydrazine hydrate (1 equivalent, 20°).1... 

Chloro-l-methylpyridinium iodide (683) functions as an important mediator in a variety of different reactions. Esters are formed in high yield from acids and alcohols when reacted with one equivalent of (683) in the presence of two equivalents of triethylamine (Scheme 158) (75CL1045). cv-Hydroxy acids are lactonized under similar conditions (76CL49). The pyridinium salt (683) will also convert thioureas into carbodiimides (77CL575) and pyridine-2-thiones to pyridyl sulfides (75CL1159). 

Treatment of amino acid 156, imine and 2-chloro-l-methylpyridinium iodide (Mukaiyama s reagent) in the presence of triethylamine in refluxing dichloro-methane afforded spiro-(3-lactams 157,158. These were obtained as a 1.8 1 mixture of diastereoisomers and separated by column chromatography. The reaction of 159 and imine under the usual experimental conditions resulted in the formation of a single diastereoisomer 160. The absolute (3 S, 4 S, 7 -configuration was assigned on the basis of mechanistic considerations and XH NMR spectra. The presence of the stereocenter affords complete diastereoselectivity (only trans diastereoisomers 157, 158) and enantioselectivity (160). 

In continuation of the research on solid-phase synthesis of biologically interesting (3-lactam compounds towards the development of combinatorial libraries, Mata et al. [102] investigated use of 2-chloro-l-methylpyridinium iodide (Mukaiyama s reagent) as a key reagent for the construction of the (3-lactam ring in a stereoselective manner. The popular explanation involves the reaction of ketene B with the imine to form a zwitterionic intermediate D (Scheme 13). Alternatively, it is the activated acid A that acylates the imine to form the zwitterion D by abstraction of proton with... 

Reduction of carboxylic acids to aldehydes. 2 3-Acyllhiazolidine-2-thiones (2) can be prepared by reaction of l,3-thiazolidine-2-thione (1) with carboxylic acids directly (using 2-chloro-l-methylpyridinium iodide, 8, 95-96) or with acid chlorides (triethylamine or DCC). They can also be prepared from reaction of the thallium salt of 1 with an acid chloride. Yields by all four methods are 70-95%. The amides are reduced to aldehydes by either DIBAH or, generally in higher yield, by NaBH4 (90-98% yield). 

Kinetic studies of the substitution reaction of 2-chloro-l-methylpyridinium iodide with phenoxides are consistent with the SnAt mechanism, with rate-determining nucleophilic attack.38 The effects of a variety of ring substituents on the reactivities of 2-fluoro- and 2-chloro-pyridines in reactions with sodium ethoxide in ethanol have been examined. The results were discussed in terms of the combination of steric, inductive, and repulsive interactions.39 Substitution in 2,4,6-trihalopyridines normally occurs preferentially at the 4-position. However, the presence of a trialkylsilyl group at the 3-position has been shown to suppress reaction at adjacent positions, allowing substitution at the 6-position.40 Methods have been reported for the introduction and removal of fluorine atoms for polyfluoropyridines. Additional fluorine atoms were introduced by metallation, chlorination, and then fluorodechlorination, while selective removal of fluorine was achieved by reduction with either metals or complex hydrides or alternatively by substitution by hydrazine followed by dehydrogena-tion-dediazotization.41... 

A novel synthesis of a-carboxyl, co-amino heterodifunctional polystyrene and its intramolecular cyclization was reported. Cyclic polystyrene with controlled size was synthesized by the intramolecular cyclization of linear a-carboxyl, co-amino heterodifunctional polystyrene under high dilution in the presence of 2-chloro-l-methylpyridinium iodide [67]. The linear precursor polymer was derived from a-diethyl acetal, co-amino heterodifunc-... 

The oxathiocin 771 was synthesized from a-(bromomethyl)acrylic acid and 3-mercapto-l-propanol in the presence of NEt3 to give - [ (3-hydroxy propy I )thio methyl [acrylic acid 792, which by an intramolecular cyclization in presence of NEt3 and 2-chloro-l-methylpyridinium iodide yielded the eight-membered ring in good yield (Scheme 155) <2005ASC1811>. 

Meanwhile, Mukaiyama et al. [26] developed another similar procedure, by the use of 6-phenyl-2-pyridyl esters, for the synthesis of macrocychc lactones. This method has been used in the synthesis of f - - )-ricinelaidic acid lactone 40) [27]. Thus, as shown in Scheme 13, a mixture of 6-phenyl-2-pyridone, 2-chloro-l-methylpyridinium iodide 28), and triethylamine in dichloromethane was stirred at room temperature for 1 h. To this solution was added a dichloromethane solution of the hydroxy acid 38 and triethylamine under reflux over 6 h to give the activated ester 39 in 99% yield. A dichloromethane solution of 39 was added to a / -toluenesulfonic acid solution in dichloromethane under reflux over 11 h. Acid-induced lactonization led to the macrocycle 40 in 96% yield ... 

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