Pyridine 3.5- disubstituted, amination

The disubstituted amines form with pyridine and trimethylamine 1 1 adducts, the stability of which increases with the degree of fluorination (59). 

Usually it is possible to isolate and characterize the arenediazonium tetrafluoroborate intermediate, e.g. 8, and then, in the next step, carry out the thermal decomposition of that intermediate, c.g. the preparation of 2.6-disubstituted 3-fluoropyridines 9 from the corresponding pyridin-3-amines 7 (Tabic 7, see also Vol. If lOa, p 711... 

Using the processes described above, complex products are obtained if a monosubstituted phenol is used instead of a 2,6-substituted material. However, by using as the amine" a 2-disubstituted pyridine such as 2-amylpyridine, more linear and, subsequently, useful polymers may be obtained. 

Carbodiimides have been prepared by desulfurization of thioureas by metal oxides, by sodium hypochlorite,4 or by ethyl chloroformate in the presence of a tertiary amine by halogena-tion of ureas or thioureas followed by dehydrohalogenation of the N,N -disubstituted carbamic chloride 8 and by dehydration of disubstituted ureas using -toluenesulfonyl chloride and pyridine.7 The method described above is a modification of that of Campbell and Verbanc. ... 

The final step to 46 is cyclocondensation of 3,7-diazabicyclo[3.3.1]nonane (51), bispidine70, with formaldehyde. There are two different approaches to 51 (i) a pyridine is converted to a piperidine and (ii) the double Mannich or Robinson-Schopf condensation of ketone 52 with formaldehyde and primary amines affords 1,5-disubstituted 3,7-dazabicyclo[3.3.1]nonan-9-one (53), bispidone, from which 5,7-disubstituted l,3-diazaadamantan-6-one (61) is derived. Route (i) is adopted by Galinovsky and Langer,71 Stetter and... 

In this review, acids and bases [8] (benzoic acids, pyridines and 1,10-phenanthrolines) will be discussed as functional groups (light bulbs). They have been incorporated into bimacrocyclic structures by bis-a- or bis-orrlio-substitu-tion of the acids or bases 2,6-disubstituted benzoic acids and pyridines, and 2,9-disubstituted 1,10-phenanthrolines were used. For the construction of the lamp shade , attention had to be paid to the components. They had to be unreactive in order not to interfere with the reactive light bulbs . Therefore, for instance amine nitrogen atoms cannot be used as bridgeheads because they may act as bases. 

A mixture of methyl 2-(p-aminophenyl)propionate (44.75 g), methallyl chloride (34 g) and pyridine (30 ml) in isopropanol (400 ml) is boiled during 30 hours. The solvent is removed in vacuo and the residue is taken up into water and ether. After separation, the organic phase is washed repeatedly with water, after which it is dried and concentrated in vacuo. The resulting oil is fractionally distilled in vacuo (0.1 mm Hg 5 g of oil essentially consisting of methyl 2-(p-aminophenyl)propionate are collected at 115°-120°C 30 g of oil consisting of a mixture of mono- (80%) and disubstituted (20%) amines is collected at 128°-130°C. This oil is used to prepare the hydrochloride, which is recrystallized from ethyl acetate, to give white crystals (22.7 g) melting at... 

The condensation reactions of 3,4-disubstituted 1,2,5-oxadiazoles can lead to heterosub-stituted analogues of benzofurazan (see Section 4.22.3.4). Recent attention has focussed on the preparation of furazanopyrazines by reaction of diaminofurazan with a-diones and of furazano-pyridazines and -pyridines from diacylfurazans with hydrazine and primary amines, respectively. 

Reaction with P-Donors. In accord with the expectations dis-cussed above, Cp2Mo2(C0K reacts readily with two equivalents of soft nucleophiles, e.g., phosphines, phosphites, CO, etc., to give exclusively the trans-products indicated in eq. 7. With one equivalent of ligand, only disubstituted product (1/2 equiv.) and unreacted 1 (1/2 equiv.) are isolated. Hence, the addition of the first ligand is the slow step (eq. 18). Complex 1 does not react with hard bases, e.g., aliphatic amines, pyridine, ethers, alcohols, or ketones. Bulky phosphines, e.g., (cyclohexyl)3P, and Ph3As or Ph3Sb also fail to react at room temperature. Rather... 

The main deficiencies with the preceding approaches are that only arylene-amines give good yields (and there are other routes to 5-arylimidazolcs), and since unsubstituted vinylamines (R = H Scheme 4.3.3) are not available this means that 4- and 5-unsubstituted imidazoles are not accessible. An alternative route involving silyl enol ethers (6) has been reported to overcome these deficiencies (Scheme 4.3.4). Silyl enol ethers can be made either by treating a ketone with chlorotrimethylsilane and triethylamine in DMF solution, or by sequential reactions of the ketone with LDA and chlorotrimethylsilane in 1,2-dimethoxyethane. This normally gives a mixture in which the less highly substituted enol ether is the major product (enolate formation is kinetically controlled) [25], When (6) is heated with an At-chloroamidine for 12-24h in chloroform solution in the presence of an equimolar amount of dry pyridine 1,2-disubstituted (5) (R = H) or 1,2,5-trisubstituted (5) imidazoles are... 

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