Product Class 13: 1,2,3-Triazoles

Scheme 26 Reaction of Diazomethane with Dimesylmethanone O-Methyloxime [62]
Ms
Ms
N
62
OMe
+ CH 2N 2
dioxane, EtOAc
0 oC, 30 min
87%
13.13.1.1.2.1.2.3 Variation 3:
From Diazoalkanes and Diarylazines
N
Ms
N
Ms
N
OMe
63
piperidine, dioxane, EtOAc
−10 to 50 oC, 3 h
50%
Ms
N
N
N
OMe
64
Aromatic aldehyde azines 65 react with aryldiazomethanes in the presence of potassium
tert-butoxide to give N-unsubstituted 4,5-diaryl-1H-1,2,3-triazoles 66 (Scheme 27). [51] The
scope of this method has yet to be demonstrated since only two symmetrical triazoles
66 are prepared by this way. The mechanism of this reaction seems to involve one 1,3-dipolar
cycloaddition followed by base elimination of an aromatic imide anion. However it
should be noted that even in the absence of the aryldiazomethanes, the aromatic aldehyde
azines (DMSO, rt) in the presence of potassium tert-butoxide (1 equiv), give the
same 4,5-diaryl-1H-1,2,3-triazoles, although in much lower yields. [51]
Scheme 27 Reaction of Aromatic Aldehyde Azines with Aryldiazomethanes in the Presence
of Potassium tert-Butoxide [51]
Ar 1 CH
N
N
65
CHAr 1
N
N
N
N Ar1 Ar1 Ar
H
1
H
FOR PERSONAL USE ONLY
432 Science of Synthesis 13.13 1,2,3-Triazoles
+ Ar 1 CHN 2
Ar 1
DMSO, rt, 24 h
Ar 1
H
N
NH
N
N Ar1 13.13.1.1.2.1.3 Method 3:
From Diazoalkanes and Heterocumulenes
t-BuOK
Ar 1
Ar 1
N
H
N
N
66 Ar 1 = Ph 92%
Ar 1 = 4-ClC 6H 4 38%
The reaction of diazoalkanes (or their organometallic derivatives) with heterocumulenes
is a versatile method for the synthesis of 1H-1,2,3-triazoles. The reactions with ketenimines,
carbodiimides, isocyanates, and isothiocyanates are performed under very mild
conditions and generally they give the desired triazoles in moderate to excellent yields.
A. C. TomØ, Section 13.13, Science of Synthesis, 2004 Georg Thieme Verlag KG