Catalytic asymmetric S-H insertion reaction of carbenoids

NRhORhCO2MeHOOPORhORhNNOOBuBuCu(MeCN)4PF6NNCu(MeCN)4PF6ClClClClORhORhNArO2SH(Ar = 4-tBuC6H4)6Rh2(S-DOSP)4(Ar = 4-CH3(CH2)10-12C6H4)7Rh2(S-TBSP)44 Rh2(5S-MEPY)45 Rh2(S-BNP)498tt Scheme 3 Table 1. Enantioselectivity of the reaction of phenyldiazoacetate and thiols with chiral Cu(I) or Rh(II) catalysts Entry Thiols 2 (R =) Cata Solvent Temp (oC) Time (h) ee(%)b Yield (%)c 1 Ph 4 CH2Cl2 rt 8 1 56 2 Ph 5 CH2Cl2 rt 4 13 49 3 Ph 5 PhH rt 5 10 60 4 Ph 5 CH2Cl2 0 8 14 52 5 Ph 5 n-hexane rt 12 5 49 6 Ph 6 CH2Cl2 0 2 21 53 7 Ph 7 CH2Cl2 0 2 23 61 8 Ph 8 CH2Cl2 rt 12 7 45 9 Ph 9 CH2Cl2 rt 12 6 39 10 2-ClPh 5 CH2Cl2 rt 4 6 47 11 2,6-(CH3)2Ph 5 CH2Cl2 rt 4 5 62 12 Cyclohexanyl 5 CH2Cl2 rt 4 6 72 aFor Cu(I) catalyst: chiral ligand (11 mol %) was mixed with Cu(MeCN)4PF 6 (10 mol %); for Rh(II) catalyst: 0.5 % mol catalyst is used. bEe’s determined by chiral HPLC; Chiracel OJ; hexane/iso-propanol. cIsolated yields. Although the enantioselectivity is rather low, we proceeded to apply the best reaction conditions in Table 1 to other aryldiazoacetates. Two Rh(II) catalysts, 5 and 7, were used, and the results are summarized in Table 2. It demonstrates that moderately low enantioselectivity can be