mechanism:
references:
Tetrahedron: Asymmetry 2007, 18, 149.J. Org. Chem. 2004, 69, 2042.Angew. Chem., Int. Ed. Engl. 2002, 41, 2024. (review)Synthesis 1986, 89.J. Am. Chem. Soc. 1980, 102, 5974. (seminal)