Synthesis of 1,3,4-thiadiazoles
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.
A transition-metal-free condensation of semicarbazide/thiosemicarbazide with aldehydes followed by I2-mediated oxidative C-O/C-S bond formation provides 2-amino-substituted 1,3,4-oxadiazoles and 1,3,4-thiadiazoles in an efficient and scalable fashion.
P. Niu, J. Kang, X. Tian, L. Song, H. Liu, J. Wu, W. Yu, J. Chang, J. Org. Chem., 2015, 80, 1018-1024.
N-Tosylhydrazones can be used as substrates for diversity-oriented synthesis of 1,2,4-triazoles, 1,3,4-thiadiazoles, and 1,3,4-selenadiazoles with NH2CN, KOCN, KSCN, and KSeCN as odorless reaction partners. Reactions in the presence of NCS include an in situ formation of N-tosylhydrazonoyl chlorides.
Z. Wei, Q. Zhang, M. Tang, S. Zhang, Q. Zhang, Org. Lett., 2021, 23, 4420-4425.
The reaction of a thiosemicarbazide intermediate with EDC·HCl in DMSO or p-TsCl, triethylamine in N-methyl-2-pyrrolidone gives the corresponding 2-amino-1,3,4-oxadiazoles and 2-amino-1,3,4-thiadiazoles through regioselcective cyclization processes.
S.-J. Yang, S.-H. Lee, H.-J. Kwak, Y.-D. Gong, J. Org. Chem., 2013, 78, 438-444.