The insertion of an aryne into a C-S bond can suppress the addition of an S nucleophile to the aryne in the presence of palladium. Catalyzed by Pd(OAc)₂, a wide range of α-carbamoyl ketene dithioacetals readily react with arynes to selectively afford functionalized 2-quinolinones in high yields under neutral reaction conditions by a C-S activation/aryne insertion/intramolecular coupling sequence. The attractive feature of the new strategy also lies in the versatile transformations of the alkythio-substituted quinolinone products.
A metal-free vinylic carbon-hydrogen bond thiolation has been developed. Under the catalysis of iodine (10 mol%), the cyclization of a-alk-A C H T U N G T R E N N U N G enoyl ketene dithioacetals afforded a broad range of polyfunctionalized 2-methylene-3-thiophenones in good selectivity with moderate to excellent yields via tandem iodocyclization and dehydroiodination. The synthetic strategy can also be extended to the cyclization of ortho-methylthiophenyl vinyl ketones leading to 2-methylene-3-benzothiophenones.
Palladium-catalyzed cyclization of β-alkylthio dienone derivatives affords 2-cyclopentenones in a regio- and stereoselective manner in the presence of silane. C-S activation, intramolecular carbopalladation and hydrogenolysis construct the cascade process.
Unique imidoylation of thioorganics with isocyanides endows an unprecedented aerobic oxidation process. Catalyzed by Pd(Ph3P)2Cl2 in the presence of Ph3SiH under N2 then upon exposure to air, a wide range of α-acyl ketene dithioacetals react with isocyanides to afford 5-hydroxy-α,β-unsaturated γ-lactams via a C-S bond activation, isocyanide migratory insertion, hydrogenation, selective aerobic oxidation, and intramolecular nucleophilic addition sequence.
A combination of palladium and silane has been well used for the catalytic desulfurative cross‐coupling reactions under neutral conditions. Catalyzed by 10 mol‐% of bis(triphenylphosphine) palladium(II) dichloride in dimethylformamide in the presence of 2 equiv. of triphenylsilane, the carbocyclizations of α‐(3‐butenoyl) ketene dithioacetals took place smoothly leading to 2‐cyclopentenones in high yields. Thus, a new Heck‐type cyclization based on C–S bond cleavage for the synthesis of spiro compounds by using silanes as the desulfurative agents has been established.
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