A ruthenium(II)-catalyzed annulation between two molecules of sulfoxonium ylides is achieved, generating a variety of substituted isocoumarins in reasonable yields. This strategy features dual C−H/C−C activation in one pot and has a wide substrate scope and good functional group tolerance.I socoumarin and its derivatives are important natural lactones, which are generally found in natural products as a basic structure. 1 It was found that compounds with an isocoumarin structure have a certain physiological activity, 2 which are widely used in the treatment of cancer, 3 allergies, 4 sterilization, 5 and other aspects. 6 In addition, they could be used as key synthetic intermediates in drug discovery. 7 Thus, the synthesis of compounds with such a skeleton has attracted great interest. 8 Among the many synthetic methods to access these compounds, the transition-metal-catalyzed C−H activation/annulation cascade reactions of benzoic acid derivatives with coupling partners represent one of the most powerful and straightforward methods to isocoumarins. However, the coupling partners are commonly limited to internal alkynes (Scheme 1a). 9 The use of coupling partners other than internal alkynes will greatly enhance the scope of metal-catalyzed synthesis of isocoumarins.Sulfoxonium ylides are carbene precursors that are easier to prepare and more stable and safer than diazonium compounds. 10 Sulfoxonium ylides have been used as alkylating reagents in a variety of reactions. 11−15 Since the first example of rhodium(III)-catalyzed C−H alkylation of arenes with sulfoxonium ylides was independently discovered by Aïssa 11 and Li, 12 sulfoxonium ylides have been widely used as alkylating reagents in transition-metal-catalyzed C−H functionalization of a range of arenes. 13 Recently, Li's work illuminated the method of synthesizing isocoumarins from Nmethoxybenzamides, using sulfoxonium ylides as coupling partners and rhodium(III) as a catalyst (Scheme 1b). 14 Subsequently, a method for the formation of isocoumarins via ruthenium(II)-catalyzed C−H activation/annulation of benzoic acids and sulfoxonium ylides was reported by Ackermann (Scheme 1c). 15 Inspired by the works of Li and Ackermann, we questioned whether sulfoxonium ylides could be able to serve as both arenes 16 and coupling partners in transition-metal-catalyzed C−H activation. As our ongoing interest in C−H activation 17 and C−C cleavage, 18 herein, we disclose a ruthenium(II)-catalyzed dual C−H/C−C activation of sulfoxonium ylides for the synthesis of isocoumarins (Scheme 1d). 19 We initiated our investigation on the model reaction of sulfoxonium ylide (1a) to optimize various reaction parameters. The results are summarized in Table 1. To our delight, under reaction conditions using [RuCl 2 (p-cymene)] 2 as the catalyst, 2,4,6-trimethylbenzoic acid (MesCO 2 H) being an additive, and Na 3 PO 4 as the base in HFIP at 110 °C under an air atmosphere for 24 h, the desired product (2a) was obtained in 78% yield (entry 1). Investigations on various solvents indicat...

A general, practical, and environmentally friendly protocol to synthesize 1,2,3‐trisubstituted 4‐quinolones from readily available ynones and sulfonamides was developed. The construction of one C−C bond and two C−N bonds via cleavage of one N−S, one C−S, and one C−X (X=F, Cl, Br, O) bond is achieved under transition‐metal‐free conditions in one step. This transformation generates 1 equiv. of sulfur dioxide and 1 equiv. of hydrogen halide as the byproducts. The broad substrate scope and functional group tolerance are demonstrated by 52 examples of 1,2,3‐trisubstituted 4‐quinolones. A preliminary mechanistic study supports a sequential Michael addition/Smiles rearrangement/N‐arylation reaction pathway.

A utility approach toward trisubstituted allenes through Pd-catalyzed alkynyl Heck coupling reaction of alkynes and aryl iodides is reported. This process proceeded via regioselective carbopalladation of 1-aryl-1-alkynes to give alkenyl palladium species, which undergo β-hydride elimination to provide 1,1-diarylallenes in 25−71% yields. This method features unique regioselectivity and high functional group compatibility.

A base-mediated semihydrogenation of ynamides using p-toluenesulfonyl hydrazide as an inexpensive and easy-to-handle hydrogen donor is reported. This transition-metal-free protocol avoids overhydrogenation and reduction of other functional groups, generating the thermodynamically unfavorable Z-enamides exclusively.

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