Pyridine 2,6-dehydro

Copper(II), di-/Lt-bromobis[bromo(pyridine)-structure, 2, 108 Copper 8-hydroxyquinolinate biocidal activity mechanism, 1, 401 fungicide, 1, 399 Copper nitrotetrazole as propellants, 5, 837 Copper phthalocyanine, 1, 333-334 colour and constitution, 1, 345 Coproporphyrin, 4, 382 Coproporphyrin, dehydro-, 4, 382... 

It was assumed that pyridine derivative 181 yielded pyrido[l,2-c]pyrimidine betaine 182 under catalytic hydrogenation conditions over (5,S)-Et-DuPHoS-Ph catalyst (99TL1211). 6,7-Dehydro derivative 184 of trequinsin (3) was obtained from pyrimidinone 183 by heating in an 1 1 mixture of MeOH and cone. HCl under reflux (97IJC(B)349). 

Six-Membered Heterocycle Ring Formation. Heterocycle formation involving diketene usually involves acetoacetylation of a substrate, followed by intramolecular condensation. Diketene itself readily dimerizes through self-condensation forming mainly dehydro acetic acid [771-03-9] (DHA) (13). Dehydroacetic acid and sodium dehydro acetate [4418-26-2] are used as preservatives for foods and cosmetics. DHA is found as an unwanted by-product in many diketene reactions, but can be obtained intentionally by dimerizing diketene in the presence of pyridine [110-86-1] in benzene, diazabicyclo[2.2.2]octane [280-57-9] (DABCO), and other basic catalysts. 

A mixture of 10.0 g of dehydro-epi-androsterone, 40 ml of pyridine and 20 ml of oenanthic acid anhydride was warmed for 2 h on a steam bath. About 10 ml of water were added and the mixture was warmed for a further 30 min. The reaction mixture was then subjected to a steam distillation. The resulting mixture was extracted with ether and the extract was successively washed with dilute sodium hydroxide solution, sodium carbonate solution and water. 

To a solution of 1 gram of 16-dehydropregnenolon-3p-acetate in 10 ml pyridine is added 0.22 gram of hydroxylamine hydrochloride, and the mixture is allowed to stand at room temperature for four days. One gram of 16-dehydropregnenolon-3p-acetate oxime is dissolved in 30 ml of hot dioxane, and then the solution is cooled in an ice bath until about one-half of the dioxane has solidified. Then 1 gram of phosphorus pentachloride is added and the mixture is shaken until all the dioxane has melted. The mixture is maintained at 35°C, for seventy-five minutes, then an excess of ice is added and the solution is again allowed to stand at 35°C. After about thirty minutes, a solution of 5 ml of concentrated hydrochloric acid in 10 ml of water is added, and the mixture is diluted with water, extracted with ether and the ethereal extract washed with dilute sodium hydroxide solution. The ether is removed on a steam bath and the residue is worked up to yield dehydro-isoandrosterone. 

Alkaline hydrolysis of 12-acetylnapelline (38) yielded an amino alcohol identical to napelline (34). This result indicated that the new alkaloid was napelline monoacetate. Treatment of 12-acetylnapelline with acetic anhydride and pyridine gave the triacetate 39. The latter was selectively hydrolyzed by alkali to afford 1-acetylnapelline (40). Oxidation of 38 with silver oxide yielded dehydro derivative 41, a result that revealed the presence of an a-hydroxy group at C-l in 38. Hydrogenation of 12-acetylnapelline over a... 

Sulphuric acid has been used for the O-demethylation of some dehydro-aporphines and 7-hydroxylated aporphines.50 Noraporphines can be separated from aporphines by trifluoroacetylation, using trifluoroacetic anhydride in pyridine. Aporphines, however, tend to be converted by this reagent into the corresponding phenanthrenes.51... 

Because of its flexibility, the Torgov synthesis (see Scheme 6) is still used quite frequently for the preparation of modified steroids. Acid cyclization of 3-methoxy-8,14-seco-oestra-l,3,5(10),9(1 l)-tetraene-14,17-dione (96) gave a mixture of the A -bisdehydro-oestrone (97) and A -dehydro-14/8-hydroxy-8a-oestrone (98). Catalytic hydrogenation of (98) afforded 3-methoxy-14 -hydroxy-8a,9)8-oestrone (99a) and 79% of 3-methoxy-14)S-hydroxy-8a,9a-oes-trone (99b). Treatment of (99b) with thionyl chloride in pyridine provided, after hydrolysis, 59% of 3-methoxy-A -dehydro-8a-oestrone (100), which on hydrogenation yielded the 8a,14)S-oestrone analogue (101). 

Dehydrosparteine diperchlorate reacts with butyl hydroperoxide in pyridine to give a 17-hydroxydehydrosparteine salt (LIX) (5S) which rearranges to a mixture of dehydro bases these in turn can be reduced to a mixture of A-formylpiperidylquinolizidine (LX) and piperidyl-quinolizidine (LXI). This is a method for opening the sparteine nucleus. 

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