Acetonitrile pyridinium chloride

A different route to pyrones is the preparative electrochemical oxidation of enamines in acetonitrile in the presence of tetraethylammonium perchlorate (88MI2) (Scheme 46). The synthesis of 2-pyrone derivatives has been carried out by reaction of /3-dicarbonyl compounds with methyl-a-benzoylamino-/3-dimethylaminoacrylate (96JHC751). Thiapyran derivatives can be obtained by interaction of enamines based on (/3-amino-a-cyanoacryloylmethyl)pyridinium chloride derivatives with carbon disulfide (95M711).The synthesis of pyridine derivatives based on analogous enamines has been described as well (95M711). 

When bicyclo[3.1.0]hexan-2-one was refluxed with pyridinium chloride in acetonitrile a mixture of 4-chlorocyclohexanone (4) and 3-(chloromethyl)cyclopentanone (5) was obtained. ... 

A comprehensive study of coated anion-exchange resins provides some valuable insights [20]. Of several coating materials tested, cetyl pyridinium chloride (CPI) was found to be the most satisfactory. Static coating was employed with 1-3 x I0 M CPCI in 3 % (v/v) acetonitrile-97 % water. Coating of a polyacrylate resin (Rohm Haas XAD-8) gave sharper chromatographic peaks for anions than the more hydro-phobic PS-DVB resin (Hamilton PRP-1). 

Powdered N-(a-benzoyloxy-p-methoxybenzyl)pyridinium chloride added at 2° with vigorous stirring to a mixture of aq. 33%-KOH and acetonitrile, the product isolated after 1 min. -> 7-p-methoxyphenyl-6-aza-2,4,6-heptatrien-l-al. Y 76%. F. e. s. R. Kuhn and E. Teller, A. 715, 106 (19681,... 

A soln. of nicotinamide in dry acetonitrile treated with 3,5-di-O-benzoyl-D-ribo-furanosyl diloride, and the product isolated after 2 hrs. 3-carbamoyl-l-(3,5-di-0-benzoyl-D-ribofuranosyl)pyridinium chloride. Y 91%. F. e. s. M. Jarman and W. C. J. Ross, Soc. (C) 1969, 199. 

Non-Aqueous Electrolytes. One approach to increasing the stability of electrochemical photovoltaic cells is to use non-aqueous electrolytes. Work on this approach (40) is divided between organic-based electrolytes (methanol, ethanol, N,N-dimethyl-formamide, acetonitrile, propi lene carbonate, ethylene glycol, te-trahydrofuran, nitromethane, tienzonitrile), and room temperature molten salts (AlCls-butyl pyridinium chloride). These studies are relatively new and final conclusions concerning the relative merits of aqueous vs. non-aqueous electrolytes have not yet been made. 

Trimethylsilyl iodide 17, which can be generated in situ by reaction of trimethyl-silyl chloride (TCS) 14 with Nal in acetonitrile [1], converts alcohols 11, in high yields at room temperature, into their iodides 773a, HI, and hexamethyldisiloxane (HMDSO) 7 [1-8, 12]. Likewise esters such as benzyl benzoate are cleaved by Me3SiCl 14/NaI in acetonitrile under reflux [Ij. Reactions of alcohols 11 with trimethylsilyl bromide 16 in chloroform or, for in situ synthesis of 16 from liBr and TCS 14 in acetonitrile and with HMDS 2 and pyridinium bromide perbromide, proceed only on heating in acetonitrile or chloroform to give the bromides 773 b in nearly quantitative yield [3, 8, 12] (Scheme 6.1). 

N-NeoDentyl)-4-DihexylaminoDvrldinium Bromide (3h) The neopentyl salt was prepared in a similar manner from neopentyl mesylate, but reaction was carried out neat at 130 for 72 hr. Higher temperatures cannot be used, due to decomposition of neopentyl mesylate. The crude product was dissolved in water, basifled to neutralize any pyridinium salt, and was washed with petroleum ether to remove amine and unreacted neopentyl mesylate. The aqueous phase was acidified with HBr, and extracted with methylene chloride, to afford crude salt. Recrystallization from 20 1 ethyl acetate/acetonitrile affords the product (mp = 169-170 ). 

Cyclization of enone (9) in hexane with boron trifluorideetherate in presence of 1,2-ethanedithiol, followed by hydrolysis with mercury (II) chloride in acetonitrile, yielded the cis-isomer (10) (16%) and transisomer (11) (28%). Reduction of (10) with lithium aluminium hydride in tetrahydrofuran followed by acetylation with acetic anhydride and pyridine gave two epimeric acetates (12) (32%) and (13) (52%) whose configuration was determined by NMR spectroscopy. Oxidation of (12) with Jones reagent afforded ketone (14) which was converted to the a, 3-unsaturated ketone (15) by bromination with pyridinium tribromide in dichloromethane followed by dehydrobromination with lithium carbonate and lithium bromide in dimethylformamide. Ketone (15), on catalytic hydrogenation with Pd-C in the presence of perchloric acid, produced compound (16) (72%) and (14) (17%). The compound (16) was converted to alcohol (17) by reduction with lithium aluminium hydride. 

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