<i>tert</i>-Butyl(2-oxo-2<i>H</i>-pyran-5-yl)carbamate as the First Chameleon Diene Bearing an Electron-Donating Substituent

Abstract

The 2(H)-pyran-2-one bearing electron-donating tert-butylcarbamate (BocNH-) group at the 5- position is a “chameleon” diene and undergoes efficient Diels–Alder cycloadditions with alkene dienophiles with both electron-rich and electron-deficient substituents. Cycloadditions afford the 5-substituted bicyclic lactone cycloadducts regardless of the electronic nature of the dienophile. However, cycloadditions with electronically matched electron-deficient dienophiles proceed faster than those with electronically mismatched electron-rich dienophiles.

Keywords

• Diels-Alder
• cycloaddition, 2(<i>H</i>)-pyran-2-one
• electron demand