Categories: Synthesis of N-Heterocycles, Synthesis of S-Heterocycles >
Synthesis of thiazoles and benzothiazoles
Recent Literature
Treatment of N,N-diformylaminomethyl aryl ketones with phosphorus
pentasulfide and triethylamine in chloroform gives 5-arylthiazoles in good yield.
The 5-aryl-1,3-thiazole core has been successfully functionalised at the
2-position to yield, over two steps, a large array of
5-aryl-2-arylsulfonyl-1,3-thiazoles.
P. W. Sheldrake, M. Matteucci, E. McDonald, Synlett,
2006, 460-462.
Endothiopeptides can easily be obtained via Ugi reaction using thio acids as
acid components. If isonitriles with an acetal group are applied, the
endothiopeptides can directly be converted into thiazoles using TMSCl-NaI
under microwave irradiation.
U. Kazmaier, S. Ackermann, Org. Biomol. Chem., 2005, 3, 3184-3187.
Lawesson’s reagent is an efficient promoter in the solvent-free
microwave-assisted synthesis of 2-substituted benzoxazoles and benzothiazoles
from carboxylic acids and 2-aminophenol or 2-aminothiophenol, respectively.
Various aromatic, heteroaromatic and aliphatic carboxylic acids react under the
conditions developed with good yields.
J. A. Seijas, M. P. Vázquez-Tato, M. R. Carballido-Reboredo, J.
Crecente-Campo, L. Romar-López, Synlett, 2007, 313-316.
Various benzothiazoles were synthesized by the intramolecular cyclization of
thioformanilides using 2,6-dichloro-3,5-dicyano-1,4-benzoquinone (DDQ) in
dichloromethane at ambient temperature in high yields.
D. S. Bose, M. Idrees, B. Srikanth, Synthesis, 2007,
819-823.
A general method for the formation of benzoxazoles and benzothiazoles via a copper-catalyzed
cyclization of ortho-haloanilides is reported. Optimal conditions for
cyclization used a catalyst combination of CuI and 1,10-phenanthroline as
ligand. The mechanism is believed to proceed via an
oxidative insertion/reductive elimination pathway through a Cu(I)/Cu(III)
manifold. The rate of reaction of ortho-haloanilides follows the order I >
Br > Cl, consistent with oxidative addition being the rate-determining step.
G. Evindar, R. A. Batey, J. Org. Chem., 2006, 71, 1802-1808.
A set of benzimidazoles, 3H-imidazo[4,5-b]pyridines, purines,
xanthines and benzothiazoles was readily prepared from (hetero)aromatic ortho-diamines or ortho-aminothiophenol and aldehydes using
chlorotrimethylsilane in DMF as a promoter and water-acceptor agent,
followed by oxidation with air oxygen.
S. V. Ryabukhin, A. S. Plaskon, D. M. Volochnyuk, A. A. Tolmachev, Synthesis, 2006, 3715-3726.
A new, mild, and efficient method for the synthesis of 2-substituted
benzothiazoles proceeds via the intramolecular cyclization of
thioformanilides by using hypervalent iodine reagents in CH2Cl2
at ambient temperature.
D. S. Bose, M. Idrees, J. Org. Chem., 2006, 71, 8261-8263.
Thionation of amides, 1,4-diketones, N-(2-oxoalkyl)amides, and N,N'-acylhydrazines
with the use of a fluorous Lawesson's reagent leads to thioamides, thiophenes,
1,3-thiazoles, and 1,3,4-thiadiazoles in high yields. The isolation of the final products is achieved in most cases by a
simple filtration.
Z. Kaleta, B. T Makowski, T. Soos, R. Dembinski, Org. Lett.,
2006, 8, 1625-1628.
