Polycyclic fused nitrogen heterocycles

Fused benzenoid heterocyclic systems including quinoxaline derivatives in an ether solvent are reduced by sodium to the corresponding antiaromatic doubly charged species <85JA1501>. These dianions represent a new class of charged species, viz., nitrogen-containing polycyclic anions. 

However, Aae can still be used in suitable cases as an indication of conformation, particularly for polycyclic compounds. Thus Aae measurements on TV-CH2X protons may be used to establish the cis or trans nature of the ring fusion in 1,3-heterocyclic systems. For example, the trans-fused perhydro-pyrido[3,2,l-iJ][3,l]benzoxazine (21) shows Aae 0.84 ppm, indicative of the anti-coplanar CH-nitrogen lone-pair geometry, whereas the cis-fused isomer (22), in which the nitrogen lone pair bisects the CH2 group, shows Aae 0.12 ppm.45... 

Mamedov VA, Nurkhametova IZ, Kotovskaya SK, Gubaidullin AT, Levin YaA, Litvinov lA, Charushin VN (2004a) Fused polycyclic nitrogen-containing heterocycles 11. 

Mamedov VA, Khafizova EA, Berdnikov EA, Levin YaA, Rizvanov IKh, Bauer I, Habicher WD (2006) Fused polycyclic nitrogen-containing heterocycles 15. 1,3-Bis... 

Mamedov VA, Zhukova NA, Beschastnova TN, Gubaidullin AT, Levin YaA, Litvinov lA (2009a) Fused polycyclic nitrogen-containing heterocycles 20. Thiazolo[3,4-a]quinoxalines from 4-hydroxy-2-phenyliminothiazolidines and C-substituted 1,2-phenylenediamines. Russ Chem Bull, IntEd 58(1) 191-202. doi 10.1007/slll72-009-0029-z... 

Mamedov VA, Kalinin AA, Gorbunova EA, Bauer I, Khabiker VD (2004a) Fused polycyclic nitrogen-containing heterocycles IX. Oxidative fusion of imidazole ring to 3-benzoylquinoxalin-2-ones. Russ J Org Chem 40(7) 1041-1046. doi 10.1023/B RUJO. 0000045201.90930.ff... 

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