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3132
Mogilaiah and Reddy
Friedlander synthesis[1–3] is an acid or base catalyzed condensation
followed by a cyclodehydration between an aromatic 2-aminoaldehyde or
ketone with the carbonyl compound containing a reactive a-methylene
group. 2-Aminonicotin-aldehyde condense readily with active methylene
compounds in the presence of base[4] or acid[5] catalysts. However, these
methods suffer harsh reaction conditions and longer reaction time.
Therefore, it is important to develop a simple and environmentally
safe, solvent free method to synthesis 1,8-naphthyridine derivatives.
In recent years organic reactions in the solid state have been attracting
the synthetic organic chemists because of their simplicity and synthetic
value.[6–9] Furthermore, the solid state reaction has many advantages:
reduced pollution, low costs, and simplicity in process and handling.
In view of this and in continuation of our interest on solid state organic
reactions,[10–13] herein, we wish to report NaF catalyzed Friedlander
condensation in the solid state at roomtemperature.
The Friedlander condensation of 2-aminonicotinaldehyde 1 with active
methylene compounds 2 in the presence of NaF in the solid state at room
temperature results in the formation of the corresponding 1,8-naphthyri-
dines 3 in high yields (Sch. 1). The reaction is fairly general, clean, rapid, and
efficient and product isolation is easy. The high yield transformations
did not formany undesirable side products. Further, it is to be noted that
highly pure products were obtained using this simple procedure and in most
cases no further purification was needed. The process is environmentally
benign. The experimental procedure is very simple. The reaction is also
expedited by microwave irradiation. Our attempt to use NaF as catalyst
for the reactions between 2-aminonicotinaldehyde 1 and active methylene
compounds which are in liquid state under the same conditions met with
failure and further work in this direction is under progress.
To the best of our knowledge, this is the first report on rapid synth-
esis of 1,8-naphthyridine derivatives using NaF as catalyst in the solid
state at roomtemperature.
In conclusion, we have demonstrated a simple and efficient procedure
involving simple workup for the preparation of 1,8-naphthyridine deri-
vatives under solid state conditions at roomtemperature. Moreover, high
O
CHO
NH2
O
C
O
C
Ar
NaF
Solid state
+
R
CH2
Ar
N
N
N
R
2
1
3
Scheme 1.