Premium
Phosphorus Pentoxide in Organic Synthesis, XXIX. Synthesis of 4‐Arylamino‐5,6,7,8‐Tetrahydro‐1 H ‐Pyrazolo[3,4‐ b ]Quinolines and the Corresponding N‐Mannich Bases
Author(s) -
Nielsen Søren V.,
Pedersen Erik B.
Publication year - 1986
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.198619861006
Subject(s) - chemistry , cyclohexanone , phosphorus pentoxide , yield (engineering) , formaldehyde , reagent , dehydrogenation , hydrochloride , mannich reaction , medicinal chemistry , organic chemistry , catalysis , materials science , metallurgy
4‐Arylamino‐5,6,7,8‐tetrahydro‐1 H ‐pyrazolo[3,4‐ b ]quinolines 2 have been synthesized from ethyl 5‐amino‐1 H ‐pyrazole‐4‐carboxylate ( 1 ) and cyclohexanone by heating in a reagent mixture of P 4 O 10 , N,N ‐dimethylcyclohexylamine, and an appropriate arylamine hydrochloride (8 – 52% yield). Reaction of 2 with formaldehyde and secondary amines afforded the Mannich bases 3 in 45 – 94% yield. Attempts to prepare the 5,6,7,8‐dehydrogenated analogues of 2 using a previously adopted method failed.