Pyridine hydro-chloride

Two one-pot procedures for the conversion of thiophencarbaldehydes into the nitriles consist in treatment with nitroethane and pyridine hydro-chloride or with hydroxylamine hydrochloride and iV-methylpyrroli-done. ° 2-Thenoylacetonitrile has been allowed to react with CS2 in the presence of sodium hydride to give the disodium salt (156), which was alkylated with various reagents. ... 

Furo(3,4-c)pyridin 7-Hydroxy-6-methyl-1,3-dihydro- -Hydro-chlorid E7b/2, 533 [4-CH3-1,3-oxazol -(- 3-(S02 —CH3)... 

This technique can be applied to prepare DL-a-fluoromethylputrescme (5-fluoropentane 1,4-diamine), a potent irreversible inhibitor of E colt ornithine decarboxylase, from 4-phthalimido-l -butyryl chloride, diazomethane, and hydro gen fluonde-pyridine [94 95]... 

The reason for this is that reaction (i) is usually much slower than (ii) and (iii) so that the main reaction appears to be (iv) (compare the preparation of tertiary butyl chloride from tertiary butyl alcohol and concentrated hydro-obloric acid, Section 111,33). If the reaction is carried out in the presence of pyridine, the latter combines with the hydrogen chloride as it is formed, thus preventing reactions (ii) and (iii), and a go( yield of the ester is g erally obtained. The differentiation between primary, secondary and tertiary alcohols with the aid of the Lucas reagent is described in Section III,27,(vii). 

Benzofuranyl)butanoic acid readily forms the acid chloride, and this undergoes intramolecular Friedel-Crafts acylation on treatment with tin(IV) chloride in carbon disulfide at room temperature, providing 1,2,3,4-tetra-hydro-l-dibenzofuranone (54%). " This intermediate has been converted to dibenzofuran by lithium aluminum hydride reduction and subsequent dehydrogenation, to 1-methyldibenzofuran by Grignard reaction and dehydrogenation, and to 1-dibenzofuranol by reaction with iV-bromosuccinimide and subsequent dehydrobromination with pyridine. 

Alternative reaction pathways exploring different synthetic possibilities have been studied. For instance, electron-rich dihydroazines also react with isocyanides in the presence of an electrophile, generating reactive iminium species that can then be trapped by the isocyanide. In this case, coordination of the electrophile with the isocyanide must be kinetically bypassed or reversible, to enable productive processes. Examples of this chemistry include the hydro-, halo- and seleno-carba-moylation of the DHPs 270, as well as analogous reactions of cyclic enol ethers (Scheme 42a) [223, 224]. p-Toluenesulfonic acid (as proton source), bromine and phenylselenyl chloride have reacted as electrophilic inputs, with DHPs and isocyanides to prepare the corresponding a-carbamoyl-(3-substituted tetrahydro-pyridines 272-274 (Scheme 42b). Wanner has recently, implemented a related and useful process that exploits M-silyl DHPs (275) to promote interesting MCRs. These substrates are reacted with a carboxylic acid and an isocyanide in an Ugi-Reissert-type reaction, that forms the polysubstituted tetrahydropyridines 276 with good diasteroselectivity (Scheme 42c) [225]. The mechanism involves initial protiodesilylation to form the dihydropyridinum salt S, which is then attacked by the isocyanide, en route to the final adducts. 

The interaction between 3 moles of nicotinic acid and 1 mole of 2-hexyl-2-(hydro-xymethyl)-1,3-propanediol in the presence of pyridine as a medium and para-toluene sulphonyl chloride as a catalyst gives rise to the formation of 1 mole of the desired ester, hepornicate and 3 moles of water are eliminated. 

Pyrroline 1-oxide added under Ng to a stirred soln. of methyl y-hydroxycroto-nate in chloroform, stirred 4 hrs. at 25°, then refluxed 12 hrs. methyl hexa-hydro-2-hydroxymethylpyrrolo[l,2-b]isoxazole-3-carboxylate (Y 80%) dissolved in anhydrous pyridine, treated at -15° with methanesulfonyl chloride, and kept 3 hrs. at 0° mesylate (Y 94%) hydrogenated 24 hrs. with 10%-Pd-on-carbon, filtered, methanol removed in vacuo, the residual oil dissolved in chloroform, and shaken with 1 ATNaOH-soln. crude methyl 2-hydroxypyrrolizidine-l-carbox-ylate (Y 95%). F. e. of the ring closure s. J. J. Tufariello and J. P. Tette, J. Org. Chem. 40, 3866 (1975). 

---