Categories: Synthesis of N-Heterocycles >
Synthesis of 3-pyrazolines
A catalytic asymmetric 1,3-dipolar cycloaddition of terminal alkynes with acyclic azomethine imines generated in situ from the corresponding aldehydes and hydrazides was realized using Cu(I)/pybox and axially chiral dicarboxylic acid cocatalysts.
T. Hashimoto, Y. Takiguchi, K. Maruoka, J. Am. Chem. Soc., 2013, 135, 11473-11476.
The use of tetrabutylammonium fluoride (TBAF) enables a versatile approach to isoxazolines and pyrazolines by the cyclization of alkyne substrates under mild reaction conditions. A deprotection/functionalization method is described, leading to a substituted pyrazoline in good diastereoselectivity.
E. Nagy, S. D. Lepore, Org. Lett., 2017, 19, 3695-3698.