Trifluoroacetaldehyde N-tosylhydrazone in [3+2] cycloaddition reaction for the synthesis of 5-(trifluoromethyl)pyrazolines
摘要
Trifluoroacetaldehyde N-tosylhydrazone used as a precursor for the in situ generation of CF3CHN2 by treatment with weak bases in safe concentration underwent [3+2] cycloaddition to electron deficient alkenes in the presence of N,N-diisopropylethylamine to give 5-(trifluoromethyl)pyrazolines in high yields. The reaction proceeded under mild conditions, tolerated a wide range of the substituents, and gave products promising for the drug design. The elaborated procedure avoided such drawbacks associated with the use of CF3CHN2 as volatility, toxicity, and explosion hazard.