Dedicated to Professor Scott Denmark on the occasion of his 65th birthday
Abstract
A regioselective magnesiation of the 2-pyrone scaffold was developed. Magnesiation
of this heterocycle by using TMPMgCl·LiCl (TMP = 2,2,6,6-tetramethylpiperidyl) followed
by trapping reactions with electrophiles such as aldehydes, allylic bromides, acid
chlorides, and aryl iodides provided functionalized 2-pyrones. Furthermore, methyl
coumalate and 3,5-dibromo-2H-pyran-2-one were zincated by using TMPZnCl·LiCl to afford zincated heterocycles,
which reacted with typical electrophiles. A second magnesiation at position C3 of
the 2-pyrone scaffold was achieved by using TMPMgCl·LiCl. Also, the zincation of the
4-pyrone scaffold at position C2 is reported, leading to functionalized 4-pyrones.
Key words
pyrone - metalation - magnesium - zinc - heterocycle functionalization
