2,2 -Biquinoline, formation

Scheme 34 Biquinoline formation in the presence of ammonium amide catalyst...

Most of the reactions with quinolines and degassed Raney nickels have been carried out at the atmospheric boiling point (above 230 C), a condition which is known to favor the formation of by-products. With quinoline and 4-methylquinoline (lepidine), however, the yields of the 2,2 -biquinolines were increased three to four times by heating in vacuo at 150° C, and it seems probable that other quinolines will behave similarly. Table II also shows that the yields of 2,2 -biquino-lines obtained under comparable conditions vary with the position of the methyl group in a fashion reminiscent of the trends observed with the pyridines (Table I). This similarity extends to the behavior of the two 2-methyl substituted quinolines studied, which undergo loss of the 2-methyl group to some extent and form traces of 2,2 -biquinolines. 

Rhodium-on-carbon has also been found to bring about the formation of 2,2 -biquinoline from quinoline, the yield and the percentage conversion being similar to that obtained with palladium-on-carbon. On the other hand, rhodium-on-carbon failed to produce 2,2 -bipyridine from pyridine, and it has not yet been tried with other bases. Experiments with carbon-supported catalysts prepared from ruthenium, osmium, iridium, and platinum have shown that none of these metals is capable of bringing about the formation of 2,2 -biquinoline from quinoline under the conditions used with palladium and rhodium. ... 

Photodehydrogenation reactions may lead to dimerization or cycli-zation. Intermolecular dehydrogenation with ultraviolet light has been recently illustrated in the formation of 2,2 - bipyridine, 6,6 -dimethyl-2,2 -bipyridine, and 2,2 -biquinoline on irradiation of pyridine, a-pico-line, and quinoline, respectively, under nitrogen in cooled quartz tubes.216... 

The formation of five-coordinate gold(III) has been demonstrated clearly in the complexes of 2,9-dimethyl-l,10-phenanthroline and 2,2 -biquinoline, which have the distorted square pyramidal structures (91) and (92). However, the structures of the ligands prevent square planar coordination, so that these examples are atypical.613-615 However, a related organometallic derivative, [AuCl(C4Ph4)(phen)], is known and has a similar distorted square pyramidal structure.616... 

Except for the formation of a mono Reissert compound from 2,3 -biquinoline and a di-Reissert compound from 6,6 -biquinoline relatively little had been done on diaza systems until recent years. 

The formation of 2,2-biquinoline from pyrolysis of quinoline suggest that the main reaction mode is thermal cracking and subsequent random polymerization to heavier molecules. 

Palladium catalysis promotes the Reformatsky reaction. Heteroaryl iodides are better substrates than bromides and chlorides. Iodine in electrophilic positions in the substrate, but not in the benzenoid position, were active in the Reformatsky reaction (277,278) (Scheme 63). Homo-coupling is the major pathway for iodo derivatives in the benzenoid position, with formation of 3,3 -biquinoline (279) (85CPB4309). 

The relatively vigorous reaction conditions required to effect vinyl substitution by heteroaryl halides under the influence of Pd-catalysis may lead to homo-coupling. The dominating reaction path in attempted alkenyl-ations of 4-iodopyrimidines was the formation of 4,4 -bipyrimidines (19) (Scheme 4 Section II.A.2). In reactions of 4-iodopyrimidines with a Pd-catalyst at 160°C, near-quantitative yields of the 4,4 -bipyrimidine were obtained (79CPB193). Also, in the reaction of 2-iodo-4-methylquinoline with Pd(OAc)2 as added catalyst, a major reaction path led to 4,4 -dimethyl-2,2 -biquinoline (Scheme 2 Section II.A.2.) (82CPB3647). 

Slany and Stang (96S1019) reported the synthesis of a series of optically pure 3,3A-disubstituted-4,4,-biquinoline derivatives. The resolution was nicely performed by formation of diastereomeric esters or amides. The absolute configurations were assigned and the configurational stability was found quite high. The substituents in position 3 and 3 were COiEt, COaH, COCl, and CN. 

The NMR data which also include /nx couplings have been collected by Pazderski for 105 complexes of Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV) as well as Pt(IV) complexes with simple azines such as pyridine, 2,2 -bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2 -biquinoline, l,2 6,2 -terpyridine and their alkyl or aryl derivatives. A short review on the formation and structure of heterocycles obtained from condensation of trifluoromethanesulphonamide with different carbonyl compounds has been written by Shainyan and Meshcheryakov. It contains NMR data including proton-proton couplings. A brief review (in Chinese) on NMR has been written by Li et al ... 

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