Copper-catalyzed aerobic C - C bond cleavage of lactols with N-hydroxy phthalimide for synthesis of lactones.
The transformation of cyclic hemiacetals (lactols) into lactones has been achieved by Cu-catalyzed aerobic CC bond cleavage in the presence of N-hydroxy phthalimide (NHPI). The present process is composed of a multistep sequence including a) formation of exo-cyclic enol ethers by dehydration; b) addition of phthalimide N-oxyl radical to the enol ethers followed by trapping of the resulting C-radicals with molecular oxygen to form peroxy radicals; c) reductive generation of oxy radicals and subsequent β-radical fragmentation to generate lactones.
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore).
Ya Lin
YL
Tnay
Shunsuke
S
Chiba
CC bond cleavage; copper; homogeneous catalysis; lactones; radicals