Enantioselective Synthesis of Dihydropyrazoles by Formal [4+1] Cycloaddition of in Situ-Derived Azoalkenes and Sulfur Ylides

Jia-Rong Chen, Wan-Rong Dong, Mathieu Candy, Fang-Fang Pan, Manuel Jörres, and Carsten Bolm

 J. Am. Chem. Soc., 2012, 134 (16), pp 6924–6927 

DOI: 10.1021/ja301196x