Categories: Synthesis of N-Heterocycles >
Synthesis of pyrazolines
A one-pot synthesis of nitrogen-containing heterocycles from alkyl dihalides and primary amines and hydrazines occurs under microwave irradiation via a simple and efficient cyclocondensation in an alkaline aqueous medium.
Y. Ju, R. S. Varma, J. Org. Chem., 2006, 71, 135-141.
Arylhydrazines regioselectively react with 3-butynol in the presence of a catalytic amount of zinc triflate to give aryl-substituted pyrazolines. The resulting products are easily oxidized in a one-pot procedure to the corresponding pyrazoles.
K. Alex, A. Tillack, N. Schwarz, M. Beller, Org. Lett., 2008, 10, 2377-2379.
Various 1-acyl-5-hydroxy-4,5-dihydro-1H-pyrazoles have been prepared in good yields from the corresponding 2-alkyn-1-ones. The resulting dihydropyrazoles undergo dehydration and iodination in the presence of ICl and Li2CO3 at room temperature to provide 1-acyl-4-iodo-1H-pyrazoles.
J. P. Waldo, S. Mehta, R. C. Larock, J. Org. Chem., 2008, 73, 6666-6670.
A novel, efficient, and general domino reaction of 2-acylaziridines with the Huisgen zwitterions furnishes 2-pyrazolines. A possible mechanism for the domino sequence is proposed.
S.-L. Cui, J. Wang, Y.-G. Wang, Org. Lett., 2008, 10, 13-16.