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DOI: 10.1055/s-1996-4331
The Synthesis and Characterisation of Chiral Atropisomeric 4,4’-Biquinolines
Publication History
Publication Date:
31 December 2000 (online)
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Homocoupling of ethyl 4-chloro-3-quinolinecarboxylate (9) with (Ph3P)2NiBr2 in the presence of zinc and tetraethylammonium iodide yields the enantiomeric diethyl (RS)-4,4’-biquinoline-3,3’-carboxylate 10. Two ways of chemical resolution are described: reaction of the (RS)-4,4’-biquinoline-3,3’-dicarboxylic acid chloride 12 with (S)-(-)-α-methylbenzylamine led to the diastereomeric amides 13a and b, which could be separated and transformed with thionyl chloride to the enantiomerically pure 4,4’-biquinoline-3,3’-dinitriles (S)-14a and (R)-14b. Reaction of 12 with (-)-menthol yielded the diastereomeric (-)-dimenthyl esters 16a and b, which could also be separated and transformed into the enantiomerically pure diethyl 4,4’-biquinoline-3,3’-dicarboxylates 10a and b.
atropisomerism - 4,4’-biquinolines - homocoupling - resolution - von Braun reaction