Pyridines thieno

Reports of examples of replacement of an oxo or hydroxy group with chlorine are confined to reactions of the pyridine ring. The [2,3-6]thieno-pyridine (126) gave the 5,7-dichloro derivative when treated with dichloro-... 

Ipso intramolecular alkylation to (93) occurs in the acid-promoted cyclization of the amino alcohols (92) with trifluoroacetic acid. Polyphosphoric acid gave the non-rearranged thieno-pyridine (94)... 

H NMR data for (252) and (255) are given in Scheme 57. As can be seen from these values, the same type of long-range coupling (J3,7) which has also been observed in furo-and thieno-pyridines is found for (252). UV data have been reported only occasionally. 4-Phenyl-4,5-borazarofuro[2,3-c]pyridine shows maxima at 224 (log e =4.217) and 263 nm (log e - 4.230) (measured in ethanol). 

The preparation of selenolopyridazines is accomplished in the usual manner by condensation of diformylselenophenes with hydrazines. Both selenolo[2,3-cf]pyridazine (432) and selenolo[3,"4-tf]pyridazine (433) are obtained in this way (72BSF3453) as crystalline compounds with m.p. 158 and 153 °C, respectively. By strict analogy with the synthesis of boron containing furo- and thieno-pyridines (Sections 3.17.2.3.1, 3.17.3.3.1), boroxazoselenolo-pyridines (e.g. 434) and borazaroselenolopyridines (435,436) could be prepared by condensation of appropriately substituted formylselenophenoboronic acids and hydroxylamine or hydrazine <72IJS(A)(2)257>. 

Exposure of the amino alcohols 113 to trifluoroacetic acid gives a rearranged intramolecular alkylation product 114 polyphosphoric acid gives the nonrearranged thieno-pyridine 115. 

Compounds 2 and 3 react with sodium hydride in THF to give the products of a Thorpe-Ziegler reaction. The procedure under more conventional conditions (KOH/DMF) results in a mixture of closo- and tV/o8-carboranyl-thieno-pyridines and -pyrimidines (Scheme 3) ... 

Barker, J. M., gem-Dithienylalkanes and Their Derivatives, 32, 83 The Thieno-pyridines, 21, 65. 

The same authors found that thieno[2,3-c - and - 3,2-c]pyridones (e.g., 58) yielded substitution products (59) when treated with hydrogen halides and hydrogen peroxide, or with nitric acid. The orientation of substitution and increased reactivity compared with the parent thieno-pyridine were ascribed to the +M effect of the hydroxy group in that tautomeric form however, it is clear that the same results would be expected from the pyridone tautomer. 

The results of the work on electrophilic substitution of thieno-pyridines confirm the general predictions of electron distribution calculations, i.e.. that substitution should occur preferentially / to the sulfur atom. Although relative rate data are lacking, qualitatively it would seem that the systems are even more resistant to attack than the isosteric quinoline and isoquinoline. 

The hetero-Cope rearrangement of the A -allyl-Ai-thiophenylenaminone 534 gives the intermediate 535, which subsequently cyclizes to the thieno-pyridine 536, Scheme 144 (73CB368). 

Reviews have appeared dealing with the synthesis of 6i/-pyrido[4,3- ]-carbazoles, thieno-pyridines, and imidazo-pyridines (and their benzo-analogues) having a bridgehead nitrogen atom. ... 

C led to metallation in the 2-position and not addition to the azomethine bond. Reaction with DMF gave the 2-formyl-derivative. The 3-lithio-derivative was obtained by halogen-metal exchange with 3-bromothieno[2,3-6]pyridine. Further studies of the chlorination and 5-oxidation of thieno[2,3-6]pyridine have been reported. The mass-spectral fragmentation patterns of a series of thieno-pyridine A -oxides, 5-oxides, and 55-dioxides have been elaborated. The reductive acetylation of nitro-thieno-pyridines has been studied. Polymethine... 

Thiophen Analogues of Quinoline.— Interest in the chemistry of thieno-pyridines is continuing. Thieno[3,2-b]pyridine has been prepared in 80% yield through the zinc-chloride-catalysed condensation of 3-aminothiophen hydrochloride with malonic aldehyde acetal. Reaction of the 2-amino-3-benzylthiophen (425) with l-nitro-2,2-bis(methylmercapto)ethylene (426) gave the thieno[2,3-b]pyndine derivative (427) in 29% yield. 5-Ethylthieno-... 

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