An NHC-catalyzed, regio- and stereoselective oxidative cyclization of o-alkynylbenzaldehydes bearing an unactivated alkyne moiety as an internal electrophile has been developed to afford phthalides and isocoumarins. A single organocatalytic system enabled two sequential C-O bond formations to take place in an atom economical manner via highly efficient dual activation. Molecular oxygen in air could be utilized as a source of an oxygen atom for the oxidation of aldehydes to the corresponding benzoic acids under our newly developed reagent system.

An efficient NHC-catalyzed domino oxidation/oxa-Michael addition reaction of 2-alkenylbenzaldehydes has been developed to afford 3-substituted phthalides bearing a C3-stereogenic center with a broad substrate scope and wide functional group tolerance. The preliminary results of the asymmetric process have been provided as well.

Au(I)-catalyzed cyclization of alkenyl carbonyl compounds leading to a variety of substituted naphthalenes has been developed. This process exploits a dual function of the Au(I) catalyst: (1) the oxophilic nature of the Au(I) catalyst, counterintuitive to the π-acidic reactivities generally associated with Au catalysts, and (2) olefin isomerization supported by the outcome of isotope scrambling experiments. It cannot be completely excluded that TfOH is a true operative catalyst in this protocol. In view of the practicality, the unnecessity of isomerically pure starting material in this reaction is particularly attractive and valuable.

It is demonstrated that two organocatalysts, achiral NHC and chiral bifunctional cinchonine, are mutually compatible and operating concurrently and effectively to promote the asymmetric domino oxidation/oxa-Michael addition reaction. This protocol allowed access to both enantiomers of a product by using two natural, inexpensive pseudoenantiomeric cinchona alkaloids, cinchonine and cinchonidine, as well as to phthalides containing a chiral quaternary carbon center in good enantioselectivities.

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Treatment of trisubstituted styrenes and β‐substituted allylic benzenes like (IIIa) and (XV) with AuCl(PPh3)/AgOTf allows access to a number of naphthalene derivatives.

NHC-Catalyzed Oxidative Cyclization Reactions of 2-Alkynylbenzaldehydes under Aerobic Conditions: Synthesis of O-Heterocycles. -Two C-O bonds are formed in one step leading to mixtures of phthalides and isocoumarins. The former are the major one in all cases except for the substrates bearing a butyl group at the alkyne moiety. The reaction tolerates a wide range of functionalities and protecting groups as Thp, Bn, and Ac remain unchanged. In the case of the silyl-substituted (VIII), no coumarins are formed but mixtures of silylated and deprotected phthalides are obtained. The reaction is also applied to pyridine-derived substrates. -(PARK, J. H.; BHILARE, S. V.; YOUN*, S. W.; Org. Lett. 13 (2011) 9, 2228-2231, http://dx.doi.org/10.1021/ol200481u ; Dep. Chem., Hanyang Univ., Seoul 133-791, S. Korea; Eng.) -R. Steudel

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