Product Class 13: 1,2,3-Triazoles

Sodium azide also adds to Æ-chloroenamines 182 (NR 2 R 3 = NMe 2, pyrrolidinyl, morpholino)
to give 1,2,3-triazoles 184 (via the Æ-azidoenamines 183) in good yields (Scheme
64). [193,194] However, with less basic Æ-chloroenamines (NR 2 R 3 = NMePh), azirines 185 are
the sole reaction products.
Scheme 64 Addition of Sodium Azide to Æ-Chloroenamines [193,194]
R 1
Cl
182
NR 2 R 3
R 1
R 1 = Me, t-Bu, Ph
183
N3
+ NaN 3
NR 2 R 3
MeCN, CCl 4
R 1
R 3 R 2 N
R 1
N
185
N
N
N
NR 2 R 3
R 3 R 2 N
R 1
N
H
N
N
184 58−84%
The addition of sodium azide to (1- and 2-acylvinyl)triphenylphosphonium salts 186 and
189 gives, respectively, acyl or alkoxycarbonyl-1,2,3-triazoles 188 and 191 (via the ylides
187 and 190) (Scheme 65). [195,196]
Scheme 65 Addition of Sodium Azide to (1- and 2-Acylvinyl)triphenylphosphonium
Salts [195,196]
Cl −
R 1
Ph3P +
186
O
R 2
NaN3, MeOH
H2O R 1 = iPr, t-Bu, Cy, cyclopropyl; R 2 = H, Et
X
Ph3P
+
−
189
R 1
Ph3P +
O
−
187
R
NaN3, H2O 1 h
−
1
O O
R 1 = Me, Et, Pr, iPr, Ph, OMe
FOR PERSONAL USE ONLY
460 Science of Synthesis 13.13 1,2,3-Triazoles
Ethyl 5-(4-Nitrophenyl)-1H-1,2,3-triazole-4-carboxylate (175); Typical Procedure: [187]
Ph3P +
CAUTION: Sodium azide can explode on heating and is highly toxic.
190
N3
R 2
N3
R 1
− PPh 3
− PPh 3
R
N
N
N
H
2
R
188 15−50%
1
O
N
R
N
N
H
191 30−95%
1
O
Diethyl (4-nitrobenzylidene)malonate (174; 2.0 g, 6.82 mmol) was added in one portion to
a soln of NaN 3 (443 mg, 6.82 mmol) in dry DMSO (10 mL) at 258C. The mixture immediately
became deep orange-brown in color and heat was evolved. After stirring for 2 h, the
mixture was poured onto an ice/water slurry (40 g). The resultant mixture was extracted
A. C. TomØ, Section 13.13, Science of Synthesis, 2004 Georg Thieme Verlag KG