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2 H ‐benzimidazoles. Part 5 . Convenient synthons for tricyclic heterocycles
Author(s) -
Cada Armin,
Kramer Walter,
Neidlein Richard,
Suschitzky Hans
Publication year - 1990
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19900730417
Subject(s) - chemistry , pteridine , synthon , diamine , azide , cyclohexane , derivative (finance) , benzimidazole , hydrolysis , tricyclic , medicinal chemistry , bicyclic molecule , stereochemistry , piperazine , organic chemistry , enzyme , financial economics , economics
The readily available 5‐nitrospiro[2 H ‐benzimidazole‐2,1′‐cyclohexane] ( 1 ) was converted into the carbonitrile 5 and the 4‐phenylthio derivative 4 . The NO 2 or the PhS substituents in 4 could be replaced regiospecifically by reaction with Me 3 SiN 3 or NaN 3 , respectively. The 5‐azido derivative 8 , resulting from NO 2 ‐group replacement was made to cyclize photolytically to give the angular spiro[cyclohexane‐imidazophenothiazine] 18 . The azide 9 obtained from the PhS replacement in 4 cyclized spontaneously to give the angular spiro[cyclohexane‐imidazobenzoxadiazole] 10 which, on reductive hydrolysis, furnished benzofurazan‐4,5‐diamine 14 . The diamine 14 was converted by conventional methods into a imidazobenzoxadiazole 15 , oxadiazoioquinoxaline 16 , and selenadiazoloxadiazole 17 . The carbonitrile 5 was converted, in simple steps, into the ‘stretched‐out’, angular pteridine and purine analogues, 25 and 28 , respectively.