A straightforward, regioselective, and step-economical ligand-free palladium-catalyzed decarboxylative functionalization of coumarin-3-carboxylic acids is devised. This protocol is compatible with a wide variety of electron-donating and -withdrawing substituents and allows for construction of various biologically important π-electron extended coumarins.

A highly regioselective and transition-metal free one-pot arylation of chromenones with arylboronic acids has been achieved employing KSO. The procedure consists of a sequence of some reactions including an arylation/decarboxylation cascade and proceeds well in aqueous media to afford biologically interesting flavones and 3-arylcoumarins. This method exhibited excellent selectivity and functional group tolerance under mild conditions. The reaction also showed perfect efficacy for the preparation of styryl coumarins.

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A Catellani reaction terminated by palladacycle amination leading to methanocarbazoles is reported. The outcome is the formation of three different Csp(3)-Csp(2)/Csp(3)-N/Csp(2)-N bonds through a Heck reaction/C-H activation/double amination cascade in one process.

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Linkages between vinylidene (=C:) and nitrenes (-N:), through methyne and its derivatives (CX), give allylic carbenonitrenes, C=(X)C-N, as a new brand of reactive intermediates, with conceivable singlet, triplet, or quintet ground states (X=H, 1, X=CH 3 , 2, X=COOH, 3, X=F, 4, X=OH, 5, X=OMe, 6, X=CF 3 , 7, X=CN, 8, and X=NH 2 , 9). High-spin quintet ( 5 A ) ground states are found for 1 and 2 at eight ab initio and DFT levels of theory. At the same levels, triplet ( 3 A ) ground states prevail for 3-8. Low-spin singlet ( 1 A ) input structures of 1, 2, and 4-9 cyclize spontaneously through optimization to their corresponding aromatic X-azacyclopropenylidenes, with multiplicities irrelevant to allylic carbenonitrenes. Researchers may aim for generating 3-8 with triplet states, or even 1 and/or 2 with quintet states, but we do not recommend going for generation of 9 with any multiplicity, and/or formation of 1-8 with singlet states.

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