Catalytic Environmentally Friendly Protocol for Achmatowicz Rearrangement.

The increasing interest in Achmatowicz rearrangement in organic synthesis calls for a more environmentally friendly protocol since the most popular oxidants m-CPBA and NBS produced stoichiometric organic side product (m-chlorobenzoic acid or succinimide). Mechanism-guided analysis enables us to develop a new catalytic method (Oxone/KBr) for AchR in excellent yield with K2SO4 as the only side product, which greatly facilitates the purification. This protocol was integrated with other transformations, leading to a rapid access to the highly functionalized dihydropyranones.