N-heterocyclic carbene catalyzed ring expansion of formylcyclopropanes: synthesis of 3,4-dihydro-alpha-pyrone derivatives.
N-Heterocyclic carbene catalyzed ring expansion of readily accessible 2-acyl-1-formylcyclopropanes was developed. With 5 mol % of triazolium salt 5 and 30 mol % of DBU, ring expansion of various 2-acyl-1-formylcyclopropanes led to 3,4-dihydro-alpha-pyrones in good to excellent yields.
Li
Gong-Qiang
GQ
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China.
Dai
Li-Xin
LX
You
Shu-Li
SL