Efficient Synthesis of γ‐Keto Esters from Enamines and EDA

Abstract

The reaction of enamines with ethyl diazoacetate (EDA) catalyzed by dirhodium and copper complexes provided γ‐keto esters in good yields. The influences of catalyst, reaction solvent, temperature, and structure of enamines on this transformation were investigated.

Keywords:

• Enamines
• ethyl diazoacetate (EDA)
• catalysis
• γ‐keto esters

Acknowledgments

Financial supports from the National Natural Science Foundation of China (Project number 20472061) and Suzhou University (Project number Q4109308) are gratefully acknowledged.

Notes

¹The yields of 2a obtained in different solvents: ClCH₂CH₂Cl, 70%; CH₂Cl₂, 52%; benzene, 62%; PhF, 72%; toluene, 38%.

²Characteristic spectral peaks of enamine 3: ¹H NMR (400 MHz, CDCl₃) δ 7.32 (d, J = 5.6 Hz, 2 H), 7.11 (t, J = 7.2 Hz, 1 H), 7.06 (t, J ₁ = 14.4 Hz, J ₂  = 8.8 Hz, 2 H), 4.75 (t, J = 7.2 Hz, 1H, –C˭CH), 4.16 (q, J = 7.2 Hz, 2 H), 3.75 (m, 4 H), 2.95 (d, J = 7.2 Hz, 2H, –CH₂–COOEt), 2.76 (m, 4 H), 1.26 (t, J = 7.2 Hz, 3 H); IR (film): 1733 cm⁻¹ (s, –CO–OEt), 1595 cm⁻¹ (s, –C˭C–).