2. The Knorr pyrazole synthesis is an
organic reaction used to convert a
hydrazine or its derivatives and a 1,3-
dicarbonyl compound to a pyrazole
using an acidcatalyst
4. Themechanism begins withan acidcatalyzedimine
formation, wherein thecaseof hydrazinederivatives
theattackcanhappen on eithercarbonylcarbon
and resultin two possible products.The other
nitrogenof thehydrazinederivativethenattacksthe
other carbonylgroup whichhas also been
protonatedbytheacidand forms a second imine
group.This diiminecompound gets deprotonated
to regeneratetheacidcatalystand providethefinal
pyrazoleproduct.
10. Mechanism of Action:
Antipyrine is thought to act primarily in the
CNS, increasing the pain threshold by
inhibiting both isoforms of cyclooxygenase,
COX-1, COX-2, and COX-3 enzymes
involved in prostaglandin (PG) synthesis.
11. Synthesis of Antipyrine:
EAA Phenylhydrazine
C
H3
OC2H5
O
O
+
NH2
N
H
Ph
Heat
Condensation
N
N
O
C
H3
Ph
+ C2H5OH
N
N
O
C
H3
Ph
H
CH3I
N
N
O
C
H3
Ph
CH3
13. Mechanism of Action:
Inhibition of prostaglandin synthesis,
primarily via inhibition of cyclooxygenase-2
(COX-2), and at therapeutic concentration
in humans, Celecoxib does not inhibit the
cyclooxygenase-1 (COX-1) isoenzyme.
16. Mechanism of Action:
Metamizole is a pro-drug, which spontaneously
breaks down after oral administration to
structurally related pyrazolone compounds.
Apart from its analgesic effect, the medication is
an antipyretic and spasmolytic agent. The
mechanism responsible for the analgesic effect
is a complex one, and most probably rests on
the inhibition of a central cyclooxygenase-3 and
activation of the opioidergic system and
cannabinoid system.