Studies on the Reaction of 4-Isoquinolinecarbonitrile and Its 2-Oxide with Cyanide Ion in Dimethyl Sulfoxide

1,1′-Biisoquinolines—Neglected Ligands in the Heterocyclic Diimine Family That Provoke Stereochemical Reflections

“…The standard works on the synthesis and properties of quinolines and isoquinolines do not contain significant details of the 1,1 -biisoquinolines [55][56][57][58]. Although a range of "exotic" methods of synthesis has been reported [55,[59][60][61][62][63][64][65][66][67][68][69], the commonest methods relevant to the bulk preparation of ligands for use in coordination chemistry are the oxidative dimerization of isoquinolines (Scheme 1a) and the coupling of 1-haloisoquinolines (Scheme 1b) [70,71]. The oxidative dimerization of isoquinoline with LDA/HMPA (LDA = Li(N i Pr 2 ), HMPA = hexamethylphosphoramide) in diethyl ether is reported to give 3 in 35-55% yield [72][73][74], better than the 26.3% yield obtained from the reaction with sodium naphthalenide [75,76] but not approaching the 87% obtained from the reaction with MgCl(TMP) (HTMP = 2,2,6,6-tetramethylpiperidine) [74].…”