The first example of dirhodium(II) complex-catalyzed asymmetric intermolecular C-H insertion with alpha-alkyl-alpha-diazoesters is described. The reaction of 1,4-cyclohexadiene with 2,4-dimethyl-3-pentyl alpha-alkyl-alpha-diazoacetates under catalysis by dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate], Rh-2(S-PTTL)(4), or dirhodium(II) tetrakis[N-tetrafluorophthaloyl-(S)-tert-leucinate], Rh-2(S-TFPTTL)(4), gave the corresponding C-H insertion products with enantioselectivities of up to 86% ee, albeit in low to modest yields.
Naemura Koichiro, Fukuda Ritsuko, Konishi Masayoshi, Hirose Keiji, Tobe Y+, J. Chem. Soc. Perkin Trans. 1, (1994) N 10, S 1253- 1256