- Chiral Hexahalogenated 4,4′-Bipyridines
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The preparation of 27 isomers of chiral hexahalogeno-4,4′-bipyridines by means of two complementary methods is described. The first one is convergent and based on the LDA-induced 4,4′-dimerization of trihalopyridines, whereas the second method is divergent and achieved through regioselective halogenation reactions of 4,4′-bipyridine-2,2′-diones. Iodine in 2,2′-positions of the 4,4′-bipyridines was introduced by a copper-catalyzed Finkelstein reaction (Buchwald procedure) performed on 2,2′-dibromo derivatives. Selected compounds of this new family of atropisomeric 4,4′-bipyridines were enantioseparated by high performance liquid chromatography on chiral stationary phases, and the absolute configurations of the separated enantiomers were assigned by using X-ray diffraction analysis. The latter revealed that various halogen bond types are responsible for crystal cohesion.
- Mamane,Peluso,Aubert,Cossu,Pale
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p. 4576 - 4587
(2016/07/06)
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- Logistic flexibility in the preparation of isomeric halopyridinecarboxylic acids
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Although there are many conceivable ways to funtionalize, and specifically carboxylate, 2-chloro-4-(trifluoromethyl)pyridine optionally at all three vacant positions, it is more straightforward to prepare only the 2-chloro-4- (trifluoromethyl)pyridine-3-carboxylic acid (1) from this precursor and the other 6-chloro-4-(trifluoromethyl)pyridine-2- and -3-carboxylic acids (2 and 3) from a different one, viz. 5-bromo-2-chloro-4-(trifluoromethyl)pyridine. In the same manner, it proved more convenient to convert 5-chloro-2-(trifluoromethyl) pyridine in only two of the corresponding acids (6 and 7) and to make the third one (8) from 3-bromo-5-chloro-2-(trifluoromethyl)pyridine as an alternative starting material. All model substrates for functionalization were readily accessible from the correspondingly substituted chloroiodopyridine through heavy halogen displacement by in situ generated (trifluoromethyl)copper. Graphical Abstract
- Cottet, Fabrice,Schlosser, Manfred
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p. 11869 - 11874
(2007/10/03)
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- 3-bromo-5-chloro-pyridines used as intermediates in the synthesis of azatetralones
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Compounds of the formula STR1 wherein R1 is hydrogen, fluoro, chloro, bromo, nitro, trifluoromethyl, C1 to C4 alkoxy, C1 to C4 alkylthio or C1 to C6 alkyl and R2 is a group of the formula STR2 wherein R3 is hydrogen or C1 to C6 alkyl, R4 is --CH=C2, --CH2 --YR5, or --COR6, R5 is hydrogen or an acid labile alcohol protecting group, Y is oxygen or sulfur, and R6 is --NR7 R8 or --OR9 wherein R7, R8 and R9 are independently selected from hydrogen or C1 to C6 alkyl, or an alkaline or alkaline earth metal salt thereof, which are intermediates in the preparation of hydantoin aldose reductase inhibitors and methods of preparing these intermediates.
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- 6-CHLORO-3,4-DIHYDRO-PYRANO [2,3-B]PYRIDINES HAVING THE R CONFIGURATION
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The present invention relates to processes and intermediates for the preparation of spiro-heteroazolones. The latter compounds are useful as aldose reductase inhibitors
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