9a£f-Quinolizines

The ultraviolet absorption spectra have been used to distinguish between the tautomers obtained by addition of dimethyl acetylene-dicarboxylate to pyridines. The 4/f-quinolizines show a band around 265 mfi. which is missing from the spectra of the 9a/f-quinolizines. Acheson and Taylor26 have successfully used this information to settle the constitution of the stable and labile adducts obtained by the action of acetylenedicarboxylic esters on pyridines. The ultraviolet spectra of the stable adducts formed by the above methods show... 

Kamienska-Trela et al. measured the different /(C,C) couplings in tetramethyl 9a f-quinolizine-l,2,3,4-tetracarboxylate and in a series of its alkyl... 

There are three possible structures for the quinolizine system, namely 2//-quinolizine (1), 4/f-quinolizine (2), and 9a//-quinolizine (3). None has been isolated as a stable species, although (2) may have a transient existence <65TL905>. A number of derivatives of these structures are known and have been reviewed <79COC(4)233>. 

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