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2. a;Che;Chem Soc Dalton Trans Org Chem,1992
3. a;Groves;Am Chem Soc Chem Soc Chem Commun,1983
4. See for example;Jiang;Chem Res Chem Lett,1997
5. a;Higuchi;Tetrahedron Lett Tetrahedron Lett Tetrahedron Lett,1989