Of collidine

This reaction consists of the condensation of two molecular equivalents of a 1,3 diketone (or a J3-keto-ester) with one equivalent of an aldehyde and one of ammonia. Thus the interaction of ethyl acetoacetate and acetaldehyde and ammonia affords the 1,4-dihy dro-pyridine derivative (1), which when boiled with dilute nitric acid readily undergoes dehydrogenation and aromatisation" to gb e the diethyl ester of collidine (or 2,4,6-trimethyl-pyridine-3,5 dicarboxylic acid (II)). For the initial condensation the solid aldehyde-ammonia can conveniently be used in place of the separate reagents. 

Fig. 41(A) and (b), p. 65) into which the ethereal extract is allowed to run from a dropping-funnel at approximately the rate at which the solvent is distilling. When the ether has been removed, fit a capillary tube and thermometer, and continue the distillation at water-pump pressure. The diethyl ester of collidine-3,5-dicarboxylic acid (II) distils as a pale golden oil, b.p. i76 178°/i4 mm. Yield, 5 g. from 6 g. of the ester (I). 

Present-day nomenclature is partly the result of the conflict and interplay of two functions the need to communicate in speech and on the printed page on the one hand, and the need for archival storage of information and its efficient, reliable retrieval. The former function came first, and laid the basis for the nomenclature most commonly used even today, and gave birth to a wealth of trivial names (i.e. names that give little or no information on structure). These were often coined on the basis of the origin of the substance, as in the case of collidine, obtained from distillation of bones in glue factories, or were derived from a special characteristic, as in the case of skatole, which has a fecal odor. Such names are short and generally euphonious, but they must be memorized they cannot be deduced from the structure. 

Note The reagent can be employed on silica gel and cellulose layers and the dipping solution can also be employed as a spray solution. The addition of collidine... 

Allylic bromination of pregnenolone acetate with dibromodi-methylhydantoin affords the 7-bromo compound (155) of undefined stereochemistry. Dehydrobromination by means of collidine followed by saponification affords the 5,7 endocyclic cis,cis-diene, 156. This compound contains the same chromophore as ergosterol, a steroid used as a vitamin D precursor. The latter displays a complex series of photochemical reactions among the known products is lumisterol, in which the stereochemistry at both C9 and Cio is inverted. Indeed, irradiation of 156 proceeds to give just such a product (158). This reaction can be rationalized by... 

The organic phase is dried over sodium sulfate and then concentrated to dryness. The thus obtained crude 6-chloro-1a-chloromethyl-A -pregnadiene-17o-ol-3,20-dione-17-acetate is heated to boiling in 20 cc of collidine for 20 minutes under nitrogen. After dilution with ether it is washed with 4N hydrochloric acid and washed with water until neutral. 

Glycosyl bromides can be used as donors in the presence of phenyl se-lenoglycoside acceptors, using silver triflate as a promoter in the presence of collidine. 

Scheme 5.55). Isomerization of the exocychc double bonds in 642 and 644, by traces of free trifbc acid formed by hydrolysis of TMSOTf 20, to give the endocychc isomers is effectively prevented by addition of smaU amounts of collidine [176]. 

A promoter of intermediate potency is iodonium di-vym-collidinc perchlorate (IDCP), which was successfully used for coupling reactive (armed) NPGs.62 A problem is that some IDCP-promoted reactions tend to stall, leaving substantial amounts of unreacted starting material, an effect probably caused by liberation of collidine during the course of the reaction. 

Fuji and Kawabata further demonstrated the utility of their catalyst by successfully achieving the KR of iV-protected cyclic cw-amino alcohols [113], Hence, by using 5 mol% of 4-PPY 29 in the presence of a stoichiometric amount of collidine in CHCI3 at room temperature, a variety of cyclic cw-amino alcohol derivatives were resolved with moderate to good selectivities = 10-21) (Table 6) [113],... 

In the case of 2,3,5-tri-O-benzoyl-D-ribofuranose (27) pyridinium poly(hydrogen fluoride) was added to a solution of in anhydrous dichloromethane and the solution was shaken at room temperature for 10 h in an atmosphere of dry argon. Anhydrous acetone was found to be equally effective in most reactions. The reaction of compound with Olah s reagent required the use of c.nhydrous acetone or anhydrous dichloromethane—collidine [1 1 (v/v)] in the case of compound 30 the addition of collidine was disadvantageous, whereas in the case of compound best results were obtained using anhydrous acetone—collidine [1 1 (v/v)] as the solvent. Compounds 32 and 33 were treated using pyridinium poly(hydrogen fluoride) as the only solvent. Reaction times varied from 2 h for compound 31 to more than 12 h for 32 and 33. 

The formation of bicarbazoles can also be achieved electrolytically in acetonitrile solution once again, at the anode, the carbazole cation radical is produced and dimerizes. The further oxidation of 3,3 -bicar-bazole under these conditions with loss of two electrons and formation of a dication-diradical was demonstrated. Anodic oxidative coupling occurs at nitrogen best in the presence of collidine, presumably via deprotonation. 

The checkers always observed a small amount of undissolved solid and began the addition of collidine when dissolution appeared to cease. 

Partition Methods. Walter (1952) devised a countercurrent distribution procedure for the fractionation of casein in a two-phase system containing water-ethanol-phenol at pH 8.2. The concentration of /3-casein increased in the phenol phase. Ellfolk (1957) employed a two-phase system consisting of collidine, ethanol, and distilled water at 20 °C. The a-caseins were concentrated in the water-rich phase, while the /3-caseins were concentrated in the collidine-rich phase. 

Several attempts have been made, especially in recent years, to oxidize saturated to unsaturated azlactones. 64 The oxidation of saturated azlactone 13 with DDQ or o-chloranil in the presence of collidine as a weak base affords the unsaturated azlactone 14 in 40-50% yield (Scheme 5). Breitholle and Stammer 65 reported the preparation of unsaturated azlactone 16 by dehydrobromination of the bromopseudoazlactone 15 (Scheme 5). The pseudoazlactones derived from Ala and Abu tend to dibrominate, but careful reaction conditions allowed their isolation in acceptable yields. 65 This procedure is applicable to the preparation of derivatives of AAla, AAbu, AVal, and ALeu. 66 ... 

Glycosidation.4 p-D-Glucosides are obtained stereospecifically by reaction of acetobromoglucose with a protected sugar in CH2C12 in the presence of Sn(OTf)2 (1 equiv.) and a base (1 equiv. of collidine, diisopropylethylamine, or 1,1,3,3-tetramethylurea). Addition of 4 A molecular sieves ensures anhydrous conditions. Yields are 30-60%. 

H-Lys(Fmoc)-Pro-Gly-Lys[Z(N02)]-Glu(OtBu)-Lys(Dde)-Pro-Gly-Lys(Aloc)-Ala-OH (1.11 g, 0.60mmol) was dissolved in DMF (600mL) and the pH adjusted to 8-9 by addition of DIPEA. HATU (0.26g, 1.1 equiv) was added and the soln was stirred at rt for 3 h. The solvent was removed under high vacuum and the residue was dissolved in TFA/CH2C12 (1 1,70mL) and allowed to stand at rt for 45 min. The soln was concentrated under reduced pressure and the residue triturated with Et20. Filtration afforded crude product yield 0.94 g purity >90%. The crude product (780 mg, -75%) was dissolved in MeCN/H20 (1 1) and the pH raised to 7-8 by addition of collidine (180 pL). Solid-phase extraction (Sep-Pak Vac cartridge, C18,15 mL) and lyophilization afforded the collidine salt of the title compound (750 mg) and was directly used for the immobilization reaction. 

Ketemimimum trifSates cyclobutanones. Triflic anhydride converts tertiary amides mainly into the salt (1), which loses triflic acid in the presence of collidine to form the keteneiminium salt 2. When generated in the presence of alkenes or alkynes, 2 undergoes [2 + 2] c ycloaddition to form cyclobutanones or cyclobutenones, respectively.1... 

The reductive epoxide opening can also be carried out using substoichiometric quantities of Cp2TiCl in the presence of collidine hydrochloride. Moreover, with D20 deuterium-labeled alcohols can easily be obtained using relatively cheap D20 as deuterium source [79]. 

The trienone (74), either by reaction with diazomethane and pyrolysis of the derived pyrazoline or by treatment with dimethylsulphoxonium methylide anion, yielded28 the 1 a,2 -methylene derivative (75). Epoxidation followed by the action of hydrogen chloride gave (77). The methylene bridge was re-formed by the reaction of collidine, the product being (76). Halogenated steroids of use in determining the metabolic fate of 16-chloro-oestrone methyl ethers and of chlormadinone acetate have been synthesized.29... 

For pyrimidine nucleosides only—add dry 2,4,6-timethylpyridine (collidine) (53 ixL, 0.4 mmol) with a dry gas-tight syringe and continue stirring at 0°C. The solution should become cloudy. For purine nucleosides—in place of collidine, add dry tri-n-octylamine (92 p,L, 0.21 mmol). 

For these complexes, the isotropic and 15N chemical shifts and the 15N chemical shift tensor elements were measured as a function of the hydrogen bond geometry. Lineshape simulations of the static powder 15N NMR spectra revealed the dipolar 2H-15N couplings and hence the corresponding distances. The results revealed several correlations between hydrogen bond geometry and NMR parameters which were analysed in terms of the valence bond order model. It was shown that the isotropic 15N chemical shifts of collidine and other pyridines depend in a characteristic way on the N-H distance. A correlation of the and 15N... 

Lactonizfltion. The salt also effects lactonization of oi-hydroxy carboxylic acids in the presence of collidine in a dilute solution of acetonitrile and ether. The yield of the lactone varies with the number of carbon atoms in the ring, but medium-sized lactones can be prepared in —50% yield. 15-Pentadecanolide is obtained in 90% yield. 

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