The synthesis of alpha'-acyloxy-alpha,beta-unsaturated cyclic ketones from
the corresponding alpha,beta-unsaturated cyclic ketones by using manganese
(III) acetate in combination with 2-chloropropionic acid followed by subseq
uent Arbuzov and intramolecular Horner-Emmons cyclization reactions provide
d a convenient synthetic pathway to various butenolides 4a-d.