Azacycl azines

Benzo-, Dibenzo-, and Other Fused Cycl[3.2.2]azines and Azacycl[3.2.2]azines 838... 

Synthetic routes to the various classes of azacycl[3.2.2]azines generally follow along very similar lines to the above. For example, l-azacycl[3.2.2]azines (imida/o[ 5,1,2-tv/] indolizines), 356, may be obtained by the [8+2] cycloaddition... 

The synthesis of 2-azacycl[3.2.2]azine (imidazo[2.1.5-c /]-indolizine), 334, by Paudler et al. <1975JOC1210> (Scheme 97) is apparently the only successful synthesis to date, and is in effect a variant of the Vilsmeier-Haack-Arnold method of Scheme 90. All attempts to synthesize the ring system by cycloadditions to imidazo[l,5- ]pyridine have been unsuccessful. 

When l-benzoyl-2-phenyl-4,8-diazapentalene (8) was treated with dimethyl acetylenedicarboxylate under dehydrogenating conditions, 1-phenyl-2-benzoyl-5,6-dicarbomethoxy-2a-azacycl[2,2,2]azine (9a) was... 

Azacycl[3,2,2] azine (19) has been prepared by the reaction sequence given in Eq. (4).21... 

The first cycl[3,2,2]azine derivative prepared in this way was 20.22 Theoretical considerations concerning the mechanism of the reaction have been presented.2311 1-Azacycl[3,2,2]azines (21)24 and 5-azacycl[3,2,2]azines (22a)25 may be obtained by the same route. 5-Azacycl[3,2,2]azines (22b)26 have been obtained recently by Vilsmeier reaction of the corresponding 5,7-dimethyl-6-azaindolizines. 

The reaction of 5-azaindolizines with dimethyl acetylenedicarboxylate gave the compounds 23 and 24. Attempts to remove a hydride ion from the dihydro-4a-azacycl[3,2,2]azines (24) failed.27... 

Azacycl[3,2,2]azines (34)38 and 6-nitrocycl[3,2,2]azine (lj) were obtained from 29 by treatment with ammonia and nitromethane, respectively.32 33... 

The ESR spectra of the radical anions of cycl[3,2,2]azine (la),53 1,4-dideuterocycl[3,2,2]azine (lo),53 6-nitrocycl[3,2,2]azine (lj)54 and 6-azacycl[3,2,2]azine (34)54 have been described and discussed in terms of simple MO theory. 

A mixture of 79% l,4-dideuteriocycl[3,2,2]azine (lo), 19% 1-deuterio-cycl[3,2,2]azine (lb) and 2% unchanged la was obtained by treating la with deuteriosulfuric acid. The structure of lo follows from the PMR spectrum and additional theoretical considerations.49 The site of protonation of 2-azacycl[3,2,2]azine (19) has been shown to be N-2 rather than C-3 by PMR spectroscopy.21... 

The UV spectrum of protonated 2-phenyl-1 -azacycl[3,2,2]azine (21) resembles that of the conjugate base24 whereas there is a large difference between the UV spectra of the protonated and the unprotonated 6-methyl-2-phenyl-5-azacycl[3,2,2]azine (22). s The arguments given above suggest that this anomaly is caused by hydrolysis of 22. 

Derivatives containing a pyrrole or thiophene-type heteroatom in the periphery may be looked at only formally as cycl[3,3,2]azines since they are isoelectronic with the cycl[3,3,3]azines described in Section V. 4,5-Dihydro-3//-2a-azacycl[3,3,2]azinium iodide (46) has been prepared, but could not be converted into 2a-azacycl[3,3,2]azine (47).62... 

Numerous azacycl[3,3,3]azines have been prepared containing nitrogen atoms in the stabilizing Impositions of the periphery. 

The l-azacycl[3,3,3]azines (54a, b) were obtained from the reaction of dialkyl acetylenedicarboxylates and the quinolizine derivatives (53a, b) which resulted from reaction of 2-pyridinoacetonitrile with 2-... 

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