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Synthesis of 4‐Aryl‐4,6‐dihydropyrimido[4,5‐ d ]pyridazine‐2,5(1 H ,3 H )‐diones from Biginelli Compounds
Author(s) -
Patra Gopal Chandra,
Bhunia Sankar Chandra,
Roy Monoj Kumar,
Pal Sudhir Chandra
Publication year - 2013
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.201200109
Subject(s) - chemistry , pyridazine , yield (engineering) , aryl , hydrolysis , salt (chemistry) , medicinal chemistry , derivative (finance) , organic chemistry , alkyl , materials science , economics , financial economics , metallurgy
Biginelli compounds 1 were first brominated at MeC(6) with 2,4,4,6‐tetrabromocyclohex‐2,5‐dien‐1‐one to give Br 2 CHC(6) derivatives 2 . The hydrolysis of the 6‐(dibromomethyl) group of 2c to give the 6‐formyl derivative 3c in the presence of an expensive Ag salt followed by reaction with N 2 H 4 ⋅H 2 O yielded tetrahydropyrimido[4,5‐ d ]pyridazine‐2,5(1 H ,3 H )‐dione ( 4c ; Scheme 1 ). However, treatment of the 6‐(dibromomethyl) derivatives 2 directly with N 2 H 4 ⋅H 2 O led to the fused heterocycles 4 in better overall yield ( Schemes 1 and 2 ; Table ).