Categories: Synthesis of N-Heterocycles, Synthesis of O-Heterocycles >
Synthesis of 1,3,4-oxadiazoles
Recent Literature
A direct access to symmetrical and unsymmetrical 2,5-disubstituted
[1,3,4]-oxadiazoles has been accomplished through an imine C-H functionalization
of N-arylidenearoylhydrazide using a catalytic quantity of Cu(OTf)2.
These reactions can be performed in air atmosphere and moisture making it
exceptionally practical for application in organic synthesis.
S. Guin, T. Ghosh, S. K. Rout, A. Banerjee, B. K. Patel, Org. Lett., 2011,
13, 5976-5979.
A facile and general protocol for the preparation of 2-amino-1,3,4-oxadiazoles
relies on a tosyl chloride/pyridine-mediated cyclization of thiosemicarbazides
that consistently outperforms the analogous semicarbazide cyclizations. Various
5-alkyl- and 5-aryl-2-amino-1,3,4-oxadiazoles have been prepared in good yields.
S. J. Dolman, F. Gosselin, P. D. O'Shea, I. W. Davies, J. Org. Chem., 2006,
71, 9548-9551.
N-Isocyaniminotriphenylphosphorane, aldehydes, and benzoic acids undergo
a one-pot, three-component reaction under mild conditions to afford
2-aryl-5-hydroxyalkyl-1,3,4-oxadiazoles in good yields.
M. Adib, M. R. Kesheh, S. Ansari, H. R. Bijanzadeh, Synlett, 2009,
1575-1578.
Symmetric and unsymmetric 1,3,4-oxadiazoles were synthesized in situ from
hydrazine hydrate and the corresponding 2-acyl-4,5-dichloropyridazin-3-ones
as acylating agents in polyphosphoric acid (PPA) or BF3ˇOEt2
in excellent yields.
Y.-D. Park, J.-J. Kim, H.-A. Chung, D.-H. Kweon, S.-D. Cho, S.-G. Lee, Y.-J.
Yoon, Synthesis, 2003, 560-564.
A simple and straightforward method for the direct carboxylation of aromatic
heterocylces such as oxazoles, thiazoles, and oxadiazoles using CO2
as the C1 source requires no metal catalyst and only Cs2CO3
as the base. A good functional group tolerance is achieved.
O. Vechorkin, N. Hirt, X. Hu, Org. Lett., 2010,
12, 3567-3569.
