Quinolizinium salts

Dibenzo[a,g]quinolizinium salts in cancer chemotherapy, 2, 571 hydroxylation, 2, 532 interaction with DNA, 2, 527 reactions... 

Dibenzo[a,g]quinolizinium salts, 5,6-dihydro-, 2, 547 Dibenzo[6,g]quinolizinium salts synthesis, 2, 565... 

Naphtho[ 1,2-h]quinolizinium salts applications, 2, 571 Naphtho[2,l-h]quinolizinium salts applications, 2, 570... 

Quinolizinium picrate, 2-bromo-1-hydroxy-synthesis, 2, 543 Quinolizinium salts... 

Westphal synthesis, 2, 566 Woodward synthesis, 2, 551, 552 Quinolizinium salts, l-acetylamino-2,3-dimethyl-oxidation, 2, 540 Quinolizinium salts, 1-amino-synthesis, 2, 541 Quinolizinium salts, 2-amino-applications, 2, 569 diazotization, 2, 542 N-substituted... 

Quinolizinium salts, 2-amino-l-hydroxy-diazotization, 2, 542 Quinolizinium salts, l-amino-3-methyl-diazotization, 2, 542 Quinolizinium salts, 2-bromo-synthesis, 2, 544 Quinolizinium salts, carboxy-anhydrides... 

Quinolizinium salts, hydroxytetrahydro-reactions, 2, 549 synthesis, 2, 555, 556 Quinolizinium salts, 1-methyl-synthesis, 2, 552 Quinolizinium salts, 2-methyl-condensation reactions, 2, 539 Ortoleva-King reaction, 2, 540 Quinolizinium salts, 4-methyl-Ortoleva-King reaction, 2, 540 Quinolizinium salts, l-oxo-l,2,3,4-tetrahydro-reactions, 2, 549 synthesis, 2, 555... 

Quinolizinium salts, 2,4,6-trimethyl-condensation reactions, 2, 539 Quinolizinones reactions, 2, 544 synthesis, 2, 567 Quinolizinones, nitro-synthesis, 2, 568 Quinolizin-4-ones nitration, 2, 529 synthesis, 2, 565 2,2 -Quinolyl... 

Reactivity of Partially Saturated Quinolizines and Quinolizinium Salts... 

An example of this displacement between a pyridine nitrogen atom and an aryl halide is shown in Scheme 21. When 2-pyridyl acetates 138 were C-acylated with 2-halobenzoyl chlorides, the enolized products 139 resulting from the reaction suffered an intramolecular nucleophilic attack of the pyridine nitrogen atom onto the ipso-position to give benzo[c]quinolizinium salts 140 as intermediates. Loss of HC1 gas from 140 afforded benzo[c]quinolizine derivatives 141 <2002JOC2082>. 

Dihydroisoquinoline reacts with the appropriate heterocycle-linked dimedone derivatives to give thiazolo-quinolizinium salts such as 467 <1995RJ0271, 1995DOC776> or pyrazoloquinolizines like 468 <1995RJC146> (Scheme 105). 

The Diels-Alder reaction between azonianthracene (61) and bis-substituted olefins to give 6,ll-ethanobenzo-[fo]-quinolizinium salts 62 was greatly accelerated by the action of microwave irradiation and, consequently, the reaction might be applicable to... 

Synthesis of a thiazolylpyridine via the Stille coupling has been reported [45, 46], Also described was a Stille coupling of a bromoquinolizinium salt 67 and 2-tributylstannylthiazole [47]. The reaction was conducted at room temperature to give a substituted quinolizinium salt... 

The first efficient Stille coupling of heteroaiomatic cations to tributyl stannyl derivatives has been reported. 2-Tributylstannylthiazole 21 was coupled with the btomoquinolizinimn salt 28, in the presence of Pd(0) / Cul catalysis, to afford the quinolizinium salt 29 in moderate yield. This method provides a good alternative to nucleophilic substitution of quinoliziniiun derivatives, which are usually very unstable in the presence nucleophilic species <990L545>. 

Evaluation of the UV-visible spectra has been used to demonstrate the formation of charge transfer complexes between the acridizinium (benzo[6]quinolizinium) ion and polycyclic aromatic hydrocarbons (78ZC33). Similar measurements have been employed to demonstrate the existence of an interaction between DNA and coralyne, a dibenzo[a,g]-quinolizinium salt (76JMC1261). 

Both 2-methyl- and 4-methyl-quinolizinium salts undergo the Ortoleva-King reaction (Scheme 37) to produce the expected pyridinium salts and these with p-dialkylamino-nitrosobenzenes were found to give nitrones (46) (65JPR(27)306). 

The reduction of a crude 4-chlorobenzo[a]quinolizinium salt by action of zinc and acetic acid made possible the transformation of benzo[a]quinolizin-4-one to benzo[a]quin-olizinium perchlorate (2) in an overall yield of 75.5% (Scheme 63) (77JOC1122). 

In a reinvestigation of earlier work (33LA(505)103) by Diels and Alder, Acheson et al. (60JCS1691) established that the stable isomer obtained by addition of two moles of dimethyl acetylenedicarboxylate to one of pyridine was the 4/7-quinolizine (96) and that this with bromine was oxidized to a quinolizinium salt (97 Scheme 65). 4iT-Quinolizines obtained from isoquinoline (62JCS748) and phenanthridine (63JCS3888) were similarly aromatized to afford benzo[a]quinolizinium (98) and dibenzo[a,c]quinolizinium ions (99) respectively. 

From the table it is clear that the synthesis has not proved useful except in the preparation of substituted quinolizinium compounds having at least one of its substituents at position 2. Beaman (51TH21000), in Woodward s laboratory, did succeed in obtaining some unsubstituted quinolizinium salts but the yields were reported to be very poor. 

As part of a study of the properties of the easily prepared salts (154 Scheme 89) (61JOC4944), it was discovered that their exposure to hydrogen peroxide in acetic acid followed by warming led to ring contraction and loss of sulfur, with formation of benzo[a]quinolizinium salts. Present evidence (62JOC4475, 66JOC978) indicates that the extrusion of sulfur occurs after the salt has been oxidized to the sulfoxide level. Despite the modest yields (Table 5), this ring contraction has preparative potential as well as theoretical interest. The variety of arenethiols (150) and 2-bromopyridines (151) available makes a variety of substituted 2-phenylthiopyridines (152) accessible as intermediates. 

Table 6 Benzo[a]quinolizinium Salts by Irradiation of Styrylpyridinium Salts (Scheme...

Although the synthesis of 6,7-dihydrobenzo[a]quinolizinium salts was claimed (52YZ1273) many years ago, it was later shown (59CPB609) that the early report was in error. The first synthesis of the 6,7-dihydro derivative was finally accomplished by Akaboshi and Kato (63YZ1067) by a modification of the Pschorr synthesis (Scheme 93). The necessary amine... 

Table 8 Synthesis of Benzo[a]quinolizinium Salts (178) by Cyclization of Quaternary Salts (177) Derived from 2-Phenylpyridine (176) and its Congeners (Scheme 97)...

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