Amino-1,6-naphthyridines diazotization

Nitration, suggested to involve nitrosation/oxidation, occurs during diazotization of some substituted 2-amino-1,8-naphthyridine derivatives (15).41 The selectivity of this process was contrasted with that of the nitronium ion reaction. 

Amino-l,5-naphthyridin-4 (1 //)-one (21) underwent diazotization to 3-diazo-nio-l,5-naphthyridin-4(1//)-one chloride (22) (substrate, Me2NCHO, 0°C, Me2CHCH2CH2ONO [, HCI/btOH [ 75%), which on irradiation gave 177-pyrrolo[3,2-b]pyridine-3-carboxylic acid hydrochloride (23) [substrate, AcOH, H20, 0°C, hv (arc lamp), h %].722... 

Amino-l,7-naphthyridin-4(l//)-one (10) underwent diazotization to give 4-oxo-3,4-dihydro-l,7-naphthyridin-3-ylidendiazonium chloride hydrochloride (11) (NaN02, HC1, 0°C 80%) and subsequent ring contraction on irradiation to afford pyrrolo[2,3-c]pyridine-3-carboxylic acid (12) (AcOH, H20, hv,... 

Ethyl 6-amino- (32, R = NH2) gave ethyl 6-cyano-7-ethoxy-l-ethyl-4-oxo-l,4-dihydro-l,8-naphthyridine-3-carboxylate (32, R = CN) (diazotization then CuS04, KCN 82%).1211... 

Amino-l,8-naphthyridin-7(8H)-one (61a) and their 3-nitro and 6-nitro derivatives (61b) and (61c) respectively can be nitrated successfully. The nitro substituent enters preferentially at position 6, i.e., formation of 62a from 61a when position 6 is already occupied by a nitro group, the second nitro group is introduced at position 3, i.e., formation of 62b from 61c (69GCI823). It has been mentioned that diazotation of 61 (R=Ph) with sodium nitrite/sulfuric acid also gives the 3-nitro derivative [97JHC1501]. This reaction proceeds via nitrozation, in which the NO+ is the attacking electrophile. 

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