Acridizinium compounds

It is now clear that acridizinium compounds and their benzo analogs are more susceptible to cycloaddition than are their quinolizinium counterparts. Fields et al. (68JOC390) showed that, even with the strong nucleophile 1,1-diethoxyethylene, 2,3-dimethylquinolizinium ion (35a) does not react. As yet the only quinolizinium derivative known to undergo cycloaddition is the anhydride (35b) of quinolizinium-2,3-dicarboxylic acid which, because of the increased electrophilicity provided by the electron-withdrawing substituents, undergoes cycloaddition even with the more moderately nucleophilic styrene to yield (36). 

Compounds with bridgehead nitrogen atoms between two six-membered rings are necessarily cationic and are therefore very unreac-tive. The positions in these molecules that are best conjugated with the positive nitrogen [e.g., the 4- and 8-positions in acridizinium (11.11)] will be the most strongly deactivated. 

The acridizinium system shown in Fig. 14b has given the best results thus far for a photodimer system. The spectra of these compounds are shown in Fig. 16. Crystals of the toluenesulfonate salt were used for the formation of gratings which had scattering efficiencies up to a few percent and could be erased completely. The gratings were written directly into the photodimer crystal by... 

Some reductively dimerized nitrogen heterocycles are oxidized anodically to their parent compounds with rupture of the C-C bond thus the dimerized product from reduction of acridizinium may be oxidized to acridizinium [39]. 

As in the earlier review1 this account will be restricted to the quinolizinium ion (1), the benzo[a]- (2), benzo [ft]- (3), and benzo[c]quinolizinium (4) ions, and to their derivatives. The quinolizones and compounds of similar structure (5) will be included, but the quinolizines (6 and 7) only where they appear as intermediates in synthesis or reaction. A number of trivial and unsystematic names have been used (pyridocolinium ion, dehydroquinolizinium ion for compound 1 acridizinium ion, 4u-azoniaanthracene for compound 3 phenanthridizinium ion for compounds 2 or 4), and numbering has also varied. Throughout this chapter the numbering will be as shown in formulas 1 to 4. 

Acridizinium salts also undergo [4+4] dimerization to yield (287) and aspects of the intramolecular interaction and reaction of the arene chromophores in compounds of type (288) with n=l-6 and 8 have been publishedf The quantum yields of the reversible intramolecular dimerization have been determined in several solvents and are reported to depend upon the value of n. Formation of the dimer arises from the intramolecular excimer and a common pericyclic transition state is assumed for the forward and back reactions. 

Some quasi-one-dimensional conductors ( KCP and the quinolinium and acridizinium TCNQ salts) display an intrinsic disorder. Apparently such a disorder does not result in a short free path, since in all given compounds there is a dielectric transition (6). The electron scattering on the impurities seems to explain the absence of the dielectric transition in the quasi-one-dimensional inorganic polymer (SN)X. 

The Diels-Alder reaction between acridizinium bromide and cyclopentadiene is typically catalyzed by cage compounds. In a seminal paper by Otto et al. [18], selection of catalysts was performed using the reaction product as a suitable TSA to select macrocycles from a dynamic library. Exposure of the dynamic combinatorial library (DCLs) based on dithiol building blocks to the product (as TSA) leads to the selection and the amplification of two hosts among all the constituents of the dynamic library (Figure 4.6). The selected cage compounds were applied as catalysts in separate experiments and, indeed, compound 7 was demonstrated to catalyze the Diels-Alder reaction between the two substrates. The reaction rate was... 

Acridizinium salts. A soln. of l-benzyl-2-(l,3-dioxolan-2-yl)pyridinium bromide (prepn. s. 995) in 48%-HBr refluxed 11 hrs. acridizinium bromide. Y 95%.— The cyclic acetal was superior to any known picolinaldehyde derivative in both the yield and quality of the product. F. e. s. G. K. Bradsher and J. G. Parham, J. Org. Ghem. 28,83 (1963) 6a-azonianaphthacenequinones, compounds being quinolizinium salts as well as quinones, s. J. Org. Ghem. 28, 1669. 

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