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.
Highly Enantioselective Cyclopropenation Reaction of 1-Alkynes with α-Alkyl-α-Diazoesters Catalyzed by Dirhodium(II) Carboxylates
Two rhodium(II) ions work together: [Rh2(S‐tbpttl)4] is an exceptionally effective catalyst for enantioselectivecyclopropenationreactions of 1‐alkynes with α‐alkyl‐α‐diazoacetates (see scheme). Cyclopropenation is preferred over alkene formation through a 1,2‐hydride shift.