Pyridines 4-dimethylaminopyridine

This preparation has been modified. 3c Compound 5 has also been prepared by using pyridine/4-dimethylaminopyridine in petroleum ether and chloroacetyl chloride in benzene. ... 

This course of the reaction was examined and supports the assignment of an inverse polarization (-)Ge-H(+) of the bond in HGeCls as compared to the (+)Si-H(-) bond in trichlorosilane HSiCb, which is known to form a 1 2 adduct with pyridine instead. Dichlorogallane was found to form 1 1 coordination compounds (HGaCl2L), where L = pyridine, 4-dimethylaminopyridine, 4-cyanopyridine, and 3,5-dimethy Ipyridine. ... 

Instead of pyridine, 4-dimethylaminopyridine can be converted into a chlorochromate, and the complex can be used to oxidize benzylic alcohols to aldehydes [530]. Also, tetrabutylammonium chlorochromate gives good yields of unsaturated and aromatic aldehydes from the respective alcohols [619]. 

The most prominent cellulose ester produced on the industrial scale is cellulose acetate. The reaction is usually performed with acetic anhydride and with sulfuric acid as a catalyst. To minimize heterogeneities, acetylation is allowed to run nearly to completion, and subsequently partial ester hydrolysis is initiated by the addition of water until a desirable solubility is achieved that corresponds to a DS of about 2.5. Such higher acyl homologues as propanoyl or butanoyl exhibit more thermoplastic properties. Many specialized esters such as chiral (-)-menthyloxyacetates, furan-2-carboxylates, or crown-ether-containing acylates have been prepared on the laboratory scale and characterized by NMR spectroscopy. Various procedures have been applied, using anhydrides and acyl chlorides as acylating agents in combination with such bases as pyridine, 4-dimethylaminopyridine (DMAP), or iV,iV -carbonyldi-imidazole. The substitution pattern of cellulose acetates has also been modified by postchemical enzymatic deacetylation. Cellulose 6-tosylates have been used as activated intermediates for nucleophihc substitution to afford 6-amino-6-deoxy, 6-deoxy, or 6-deoxy-6-halo-celluloses. ... 

Scheme 4.5 Synthesis of (-I-) KDO (a) r M2O. vigorous stirring, then Ac20/pyridine/4-dimethylaminopyridine, 79% (b) 03/methylene chloride -78°C to rt, then column chromatography 67%.

Scheme 4.9 Synthesis of higher carbon sugars (a) in/aiiyi bromide, uitrasound (b) Ac20/pyridine/ 4-dimethyiaminopyridine (c) OSO4, Ki04 (d) TBAF (e) H+/HC(OEt)3 (f) OSO4, A/-methyimorphoiine A/-oxide (g) Ac20/pyridine/4-dimethylaminopyridine (h) NaOMe/MeOH (i) H+.

Vinylpyridine (23) came into prominence around 1950 as a component of latex. Butadiene and styrene monomers were used with (23) to make a terpolymer that bonded fabric cords to the mbber matrix of automobile tires (25). More recendy, the abiUty of (23) to act as a Michael acceptor has been exploited in a synthesis of 4-dimethylaminopyridine (DMAP) (24) (26). The sequence consists of a Michael addition of (23) to 4-cyanopyridine (15), replacement of the 4-cyano substituent by dimethylamine (taking advantage of the activation of the cyano group by quatemization of the pyridine ring), and base-cataly2ed dequatemization (retro Michael addition). 4-r)imethyl aminopyri dine is one of the most effective acylation catalysts known (27). 

These rate constants are for the hydrolysis of cinnamic anhydride in carbonate buffer, pH 8.45, total buffer concentration 0.024 M, in the presence of the catalysts pyridine, A -methylimidazole (NMIM), or 4-dimethylaminopyridine (DMAP). In the absence of added catalyst, but the presence of buffer, the rate constant was 0.005 24 s . You may assume that only the conjugate base form of each catalyst is catalytically effective. Calculate the catalytic rate constant for the three catalysts. What is the catalytic power of NMIM and of DMAP relative to pyridine ... 

DMAP = 4-dimethylaminopyridine (10" times more effective than pyridine)... 

In place of N-methylimidazole (Melm), only dimethylaminopyridine (DMAP) could be substituted. The solid-supported amines piperidinomethyl- or morpholinomethyl polystyrene resins, pyridine, and tertiary amines like triethylamine andN-methylmorpholine were not effective. 

The donor-acceptor formation can be considered by transfer of electrons from the donor to the acceptor. In principle one can assume donor-acceptor interaction from A (donor) to B (acceptor) or alternatively, since B (A) has also occupied (unoccupied) orbitals, the opposite charge transfer, from B to A. Such a view refers to mutual electron transfer and has been commonly estabUshed for the analysis of charge transfer spectra of n-complexes [12]. A classical example for a donor-acceptor complex, 2, involving a cationic phosphorus species has been reported by Parry et al. [13]. It is considered that the triaminophosphines act as donor as well as an acceptor towards the phosphenium cation. While 2 refers to a P-donor, M-donors are in general more common, as for example amines, 3a, pyridines, 3b, or the very nucleophilic dimethylaminopyridine (DMAP) [ 14], 3c. It is even a strong donor towards phosphorus trichloride [15]. 

Figure 25 Synthesis of naturally occuring phenylpropenoid (3-D-glucopyranosides. (a) allyl alcohol/immobilized (3-glucosidase with ENTP-4000, (b) Ac20/4-dimethylaminopyridine/pyridine, (c) organoboron reagents/Pd(OAcyCu(OAc)2/LiOAc/DMF, (d) K2C03/Me0H.

An even stronger catalytic effect is obtained when 4-dimethylaminopyridine (DMAP) is used.104 The dimethylamino group acts as an electron donor, increasing both the nucleophilicity and basicity of the pyridine nitrogen. 

Photocycloaddition of cyclopentene (116) to the trimethylsilyl ether (117) gave 2 stereoisomers (118) and (119). When (118) was reduced with LiAlH4 in Et20, followed by treatment will MsCl, pyridine and dimethylaminopyridine (DMAP), the silyl ether (120) was obtained. Finally, (120) was allowed ro react with KF in the presence of [18]-crown-6 in CH2C12, as a result, hexahydroazulenone (121) was isolated41 >. On the other hand, the cyclobutane (119) could also be converted similarly to (121) in an overall yield of 47 % 41K... 

The alternative method for making activated esters is base-catalyzed transesterification. Fmoc-amino acids are esterified in excellent yields by reaction with pentafluorophenyl trifluoroacetate at 40°C in the presence of pyridine (Figure 7.13). A mixed anhydride is formed initially, and the anhydride is then attacked by the pentafluorophenoxy anion that is generated by the pyridine. Succinimido, chlorophe-nyl, and nitrophenyl esters were made by this method when it was introduced decades ago. A unique variant of this approach is the use of mixed carbonates that contain an isopropenyl group [Cf C CfyO-COjR]. These react with hydroxy compounds in the presence of triethylamine or 4-dimethylaminopyridine (see Section 4.19) to give the esters and acetone.30 35... 

FIGURE 8.15 Alkylamines encountered in peptide synthesis. 1, pyridine 2, 2,4,6-trimethylpy-ridine 3, 2,6-di-ferf-butyl-4-methylpyridine 4, 4-dimethylaminopyridine 5, A-methyl-morpholine, 6, fV-methylpiperidine 7, triethylamine 8, diisopropylethylamine 9, l-diethylaminopropane-2-ol 10, dicyclohexylamine 11, diethylamine 12, piperidine 13, piperazine 14, morpholine 15, l,8-diazabicyclo[5.4.0]undec-7-ene 16, 4-(aminoethyl)piperidine 17, frw(2-aminoethyl)amine 18, 3-dimethylaminopropylamine 19, methylamine 20, dimethy-laminoethane-2-ol 21, 1,2,2,6,6-pentamethylpiperidine 22, l,4-diazabicyclo[2,2,2]octane 23, 7-methyl-1,5,7-triazabicyclo[4,4,0]dec-5 -ene. 

It seems reasonable that polyester cyclics could be prepared by an extension of the /wendo-high-dilution [17] chemistry used for the preparation of cyclic carbonate oligomers [18, 19] however, such proved not to be the case. Brunelle et al. showed that the reaction of terephthaloyl chloride (TPC) with diols such as 1,4-butanediol did not occur quickly enough to prevent concentration of acid chlorides from building up during condensation [14]. Even slow addition of equimolar amounts of TPC and butanediol to an amine base (triethylamine, pyridine or dimethylaminopyridine) under anhydrous conditions did not form cyclic oligomers. (The products were identified by comparison to authentic materials isolated from commercial PBT by the method of Wick and Zeitler [9].)... 

Kinetic evidence has been obtained for ion-pair formation when the effects of inorganic salts on the alkaline hydrolysis of A(-phthaloylglycine (188) were investigated. Kinetic studies have been reported of acetyl transfer in acetonitrile from N-acetyloxypyridinium cations (189) to 4-(4 -A(,A(-dimethylaminostyryl)pyridine A(-oxide (190), pyridine A(-oxide (191) and 4-dimethylaminopyridine (192). In a follow-up... 

While it has been known for some time that pyridine-1-oxides are protonated on oxygen (Gardner and Katritzky, 1957), amino-pyridine-1-oxides have attracted more attention recently. Using the Hammett equation, it was concluded that the cation of 3-amino-pyridine-1-oxide was an equilibrium mixture of O- and N-protonated forms in the ratio 8 1 (Jaffe, 1965), A similar conclusion was reached for 3-dimethylaminopyridine-l-oxide (Forsythe et al.,... 

Protection of an alcohol function by esterification sometimes offers advantages over use of acetal or ether groups. Generally, ester groups are stable under acidic conditions. Esters are especially useful in protection during oxidations. Acetates and benzoates are the most commonly used ester derivatives. They can be conveniently prepared by reaction of unhindered alcohols with acetic anhydride or benzoyl chloride, respectively, in the presence of pyridine or other tertiary amines. 4-Dimethylaminopyridine (DMAP) is often used as a catalyst. The use of A-acylimidazolides (see Section 3.4.1) allows the... 

Dimethylaminopyridine HIGHLY TOXIC Pyridine. 4-(dimethylamino)- (8) 4-Pyridinamine, N,N-dimethyl- (9) (1122-58-3)... 

Note the key role of the 2-cyanopyridine ion in promoting the course of the subsequent fragmentation. Proximity effects in 2-substituted pyridines are often instrumental in dictating the nature of decomposition on electron impact, for example in 2-dimethylaminopyridine (68TL3689,73CS(3)139,74JOC285) and in other amino, chloro, and -one derivatives (68JHC647). 

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