The document summarizes three organic name reactions - Combes quinoline synthesis, Knorr pyrazole synthesis, and Pinner pyrimidine synthesis - and their respective mechanisms. The Combes quinoline synthesis involves the condensation of anilines and β-diketones to form quinolines via an acid-catalyzed ring closure. The Knorr pyrazole synthesis converts hydrazines or derivatives with 1,3-dicarbonyl compounds to pyrazoles using an acid catalyst in a three step mechanism. The Pinner pyrimidine synthesis involves the condensation of 1,3-dicarbonyl compounds with amidines catalyzed by acids or bases

1. Combes quinoline synthesis
Knorr pyrazole synthesis
Pinner Pyrimidine Synthesis
Organic Name Reaction
With Their Respective
Mechanism

2. Combes quinoline synthesis

3. Combes quinoline synthesis
The Combes quinoline synthesis is a chemical reaction, which was first reported by
Combes in 1888. It involves the condensation of unsubstituted anilines (1) with β-
diketones (2) to form substituted quinolines (4) after an acid-catalyzed ring closure of an
intermediate Schiff base (3)

4. M e c h a n i s m

5. The reaction mechanism undergoes three major steps,
The first one being the protonation of the oxygen on the carbonyl in the β-diketone, which
then undergoes a nucleophilic addition reaction with the aniline. An intramolecular proton
transfer is followed by an E2 mechanism, which causes a molecule of water to
leave. Deprotonation at the nitrogen atom generates a Schiff base, which tautomerizes to
form an enamine that gets protonated via the acid catalyst, which is commonly
concentrated sulfuric acid (H2SO4).
The second major step, which is also the rate-determining step, is the annulation of the
molecule.
Immediately following the annulation, there is a proton transfer, which eliminates the
positive formal charge on the nitrogen atom, resulting in the end product of a
substituted quinoline.

6. Knorr pyrazole synthesis

7. Knorr pyrazole synthesis
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 acid catalyst.

8. The mechanism begins
with an acid catalyzed
imine formation, where
in the case of hydrazine
derivatives the attack can
happen on either carbonyl
carbon and result in two
possible products.
The other nitrogen of
the hydrazine derivative
then attacks the other
carbonyl group which has
also been protonated by
the acid and forms a
second imine group.
This diimine compound
gets deprotonated to
regenerate the acid
catalyst and provide the
final pyrazole product.

10. Pinner Pyrimidine Synthesis

11. The condensation of 1,3-dicarbonyl compounds with amidines catalyzed by
acids or bases to give pyrimidine derivatives is regarded as the Pinner
pyrimidine synthesis
1,3-dicarbonyl
compounds
amidines
acids or
bases
Pyrimidine derivatives
1 2
3
P i n n e r P y r i m i d i n e S y n t h e s i s
D e s c r i p t i o n

12. What is Amidines ?
Amidines
Amidines are a class of oxoacid derivatives
Amidines are much more basic than amides and are the
strongest unionizedbases

13. The condensation of acetylacetone, methyl acetoacetate, or dimethyl malonate
with acetamidine has been studied by Katritzky et al. and the reaction
mechanisms for these processes have been proposed by these authors.’
AcetamidineMethyl acetoacetate
condensationHCl
2,6-dimethyl-4-hydroxylpyrimidine
M e c h a n i s m