N-Methyl-4- -pyridinium iodide

DMII = N,N-dimethyl imidazohum iodide DEII = N,N-diethyl imidazohum iodide BMII = N-butyl-N-methyl imidazohum iodide [Etpy]I = N-ethyl pyridinium iodide [pyMe]I = N-methyl pyridinium iodide MTOPI = methyl trioctyl phosphonium iodide [BusPMe] = methyl tributyl phosphonium iodide. 

General Procedure for Batch Carbonylation of Methanol in the Absence of Methyl Iodide. A complete set of procedures appears in ref. 5 bnt the following procedure is representative of a methanol carbonylation. To a 300 mL Hastelloy C-276 autoclave was added 0.396 g (1.5 mmol) of RhCl3 3H20, 112.0 g (0.507 mol) of N-methyl pyridinium iodide, 30.0 g (0.5 mol) of acetic acid, and 64.0 g (2.0 mol) of methanol. The mixture was heated to 190°C under 250 psi (1.72 MPa) of 5% hydrogen in carbon monoxide. Upon reaching temperatnre the gas feed was switched... 

Size-quantized CdS was grown in the xerogels Acidic TiO gels, doped by 4-(dimethylamino)-4 nitro-sostilbene and 4 (2-(4-hydroxyphenyl)ethenyl)-N-methyl-pyridinium iodide, were spread on a spinning ITO glass plate. Another ITO plate was placed on the field and an electric field was applied prior to drying in a vacuum. Second-order optical activity was observed 113 114... 

Other Names 4-[p-(Dimethylamino)styryl]-l-methyl-pyridinium iodide Pyridinium, 4-[2-[4-(dimethylamino) phenyl]ethenyl]-l-methyl-, iodide Pyridinium, 4-[p-(di-methylamino)styryl] -1 -methyl-, iodide 4- [2- [4-(Dimethy-lamino)phenyl]ethenyl]-l-methylpyridinium iodide 4-[4-(Dimethylamino)-a-styryl]-1 -methylpyridinium iodide 4- [4-(Dimethylamino)styryl]-1 -methylpyridinium iodide 4- [4- (Dimethylamino) styryl] -A-methylp3nidinium iodide 4 -Dimethylamino-l-methylstilbazolium iodide 4 -Di-methylamino-N-methyl-4-stilbazolium iodide D 288 ... 

The Mukaryama reagent,18 N-methyl-2-chloropyridinium iodide (6). transforms carboxylic acid 5 into the amide 7 The acid Is first activated in situ in the form of pyridinium salt 17 by an SN reaction with the Mukoixama reagent (6). This activation is a result of preventing resonance stabilization of the C-O double bond in the positively charged aryl ester 17. 

In contrast to the ease of N-functionalization, shown in Scheme 1, the triazolopyridine nucleus is resistant to direct nuclear oxidation or electrophilic additions. Electrophilic additions will occur on aryl substituents for example, nitration of l-phenyltriazolo[4,5-c]pyridine (26) and sulfonation of 2-phenyl-2i/-triazolo[4,5-6]pyridine (28) occur exclusively in the para position of the phenyl ring <34LA(514)279, 38MI 710-01). Nuclear functionalization was observed when l-( -butyl)-5-methyl-tri-azolo[4,5-c]pyridinium iodide (30) was treated with potassium ferricyanide to afford triazolopyridin-4-one (31), as shown in Scheme 2. Similarly, the iodide (30) is converted by either phosphorus oxychloride-phosphorus pentachloride, or bromine or nitric acid to 7-substituted triazolopyridin-4-ones (32) <37LA(529)288>. 

Z values have been widely used to correlate other solvent-sensitive processes with solvent polarity, e.g. the a absorption of haloalkanes [61], the n n and n n absorption of 4-methyl-3-penten-2-one [62], the n n absorption of phenol blue [62], the CT absorption of tropylium iodide [63], as well as many kinetic data (Menschutkin reactions, Finkelstein reactions, etc. [62]). Copol5mierized pyridinium iodides, embedded in the polymer chain, have also been used as solvatochromic reporter molecules for the determination of microenvironment polarities in synthetic polymers [173]. No correlation was observed between Z values and the relative permittivity e, or functions thereof [317]. Measurement of solvent polarities using empirical parameters such as Z values has already found favour in textbooks for practical courses in physical organic chemistry [64]. 

Pyridinium iodide, 4,4 (l,3,4-thiadiazole-2,5-diyl)-bis(l-methyl)-reduction, 6, 564 Pyridinium ion, N-methyl-as metabolite of pyridine, 1, 234 Pyridinium ions hydrogen bonding to water mass spectrometry, 2, 135 magnetic circular dichroism, 2, 129 NMR, 2, 121... 

An excellent example of counterion influence is the quite different thermal behavior of double-chain l-methyl-3,5-bis(n-hexadecyloxycarbonyl)pyridinium ion in crystals with iodide or chloride as counterion [4]. The iodide salt revealed three phase transitions solid crystalline-solid crystalline at —326 K, solid crystalline-liquid crystalline at —358 K, and liquid crystalline-isotropic liquid at —378 K. The X-ray diffraction pattern of the liquid crystalline phase could be best rationalized in terms of a smectic-H phase. The chloride anion could be unfavorable for liquid crystalline behavior because of its smaller ionic radius relative to the iodide anion. Less shielding of the positive charges of the pyridinium rings by the chloride counterion leads to increased electrostatic repulsion between headgroups. 

FIGURE 6.5 UV-Vis spectroscopic data for the aromatic and quinoide forms of 2-OH derivatives (1) l-methyl-4-[2-(2-hydroxyphenyl)ethenyl]-pyridinium iodide, (2) 1-methyl-4-[2-(2-oxocyclohexadienyliden)ethylidene-l,4-dihydropyridine, (3) l-decyl-4-[2-(2-hy-droxyphenyl)ethenyl]-pyridinium iodide, and (4) l-decyl-4-[2-(2-oxocyclohexadienylide n)ethyliden]-l,4-dihydropyridine. 

Cyanides can react with 1-aminopyridinium salts to give 2-substituted triazolopyridines, possibly via the pyridinium ylide. With 1-aminopyridinium iodide and cyanide ion the intermediate 4-cyanopyridine reacts with the aminopyridinium salt to give 2-(4-pyridyl)triazolopyridine (45).51 When acetonitrile or benzonitrile are used, 2-methyl- and 2-phenyltriazolo-pyridines are obtained.58 60 The reaction is thought to involve a dipolar cycloaddition of the N- mi nopyridine with the nitrile, as shown in Eq. (4). 

Alkylation of 3-methylimidazo[4,5-h]pyridine (88) with alkyl halides occurred at N-1 to give the quaternary salts (89) (68KGS954, 73KGS570, 73KGS1686), whereas methylation of the 1-methyl isomer (90) gave the l,4-dimethylimidazo[4,5-h]pyridinium chloride (91) or iodide... 

The silylated methyl ester was then a-methylated with lithium diisopropylamide and methyl iodide in tetrahydrofuran. Reduction of methyl 10-( erl-butyldimethylsilyloxy)-2-methyldecanoate with DIBAL in ether at -78°C afforded the corresponding aldehyde. The 10- tert-butyldimethylsilyloxy)-2-methyldecanal was subsequently coupled in a Wittig reaction with 1-hexyltriphenylphosphonium bromide and n-butyllithium affording (Z)- and ( )-1 -(teri-butyldimethylsilyloxy)-9-methyl-10-hexadecene in a 9 1 ratio, respectively. Deprotection with tetrabutylammonium fluroride (TBAF) in tetrahydrofuran and final oxidation with pyridinium dichromate (PDC) in dimethylformamide resulted in a 9 1 mixture of (Z)- and ( )-9-methyl-10-hexadecenoic acid as shown in Fig. (7). As was also the case with acid 6, the stereochemistry at C-9 in 7 is not known. The key step in the synthesis of the allylic methyl group was a-methylation of a methyl ester, followed by reduction to the corresponding aldehyde, which was used in the subsequent Wittig reaction. 

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