Miscellaneous Lactone Syntheses Involving CO

A variety of highly Lewis acidic metal salts have been used to catalyze intramolecular hydrocarboxylation, including Ag(I), Pd(II), Au(I), Hg(II), Rh(I), Ni(II), 

Since aikenes and aikynes can be prepared via Heck and Sonogashira reactions, respectively, tandem processes are also possible for lactone synthesis [71-77]. Appropriately, o-iodobenzoic acids can generate both phthalide and isocoumarin derivatives under Pd catalysis, with a Cul co-catalyst favoring the former and 

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