Efficient One‐Pot Multifunctionalization of Alkynes en Route to α‐Alkoxyketones, α‐Thioketones, and α‐Thio Thioketals by using an Umpolung Strategy

The use of polarized synthons is a highly desirable strategy, as it generally enables unprecedented retrosynthetic disconnections for the synthesis of unique substances. Herein, a new approach for α-oxygenated ketones, α-thioketones and α-thio thioketals via an intermolecular umpolung reaction between nucleophiles (alcohols/thioalcohols) and N-alkenoxypyridinium salts, which were generated from the corresponding alkynes, has been developed for the first time. The reactions proceed with good substrate scope and excellent functional group tolerance in one-pot manner. Applications of the products, α-oxygenated ketones, to the synthesis of other valuable synthetic moieties has also been successfully achieved.