Intramolecular Tsuji-Trost-type Allylation of Carboxylic Acids: Asymmetric Synthesis of Highly π-Allyl Donative Lactones.

Tsuji-Trost-type asymmetric allylation of carboxylic acids has been realized by using a cationic CpRu complex with an axially chiral picolinic acid-type ligand (Cl-Naph-PyCOOH: naph = naphthyl, py = pyridine). The carboxylic acid and allylic alcohol intramolecularly condense by the liberation of water without stoichiometric activation of either nucleophile or electrophile part, thereby attaining high atom- and step-economy, and low E factor. This success can be ascribed to the higher reactivity of allylic alcohols as compared with the allyl ester products in soft Ru/hard Brønstead acid combined catalysis, which can function under slightly acidic conditions unlike the traditional Pd-catalyzed system. Detailed analysis of the stereochemical outcome of the reaction using an enantiomerically enriched D-labeled substrate provides an intriguing view of enantioselection.