mechanism:

example:

references:

- Acc. Chem. Res. 2000, 33, 325.
- Curr. Org. Chem. 2000, 4, 305.
- J. Am. Chem. Soc. 1995, 117, 5120.
- Chem. Rev. 1992, 92, 1021.
- Angew. Chem. 1984, 96, 840.
- Angew. Chem., Int. Ed. Engl. 1969, 8, 556. (review)