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.
Abstract:The insertion of an aryne into a C À 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 a-carbamoyl ketene dithioacetals readily react with arynes to selectively afford functionalized 2-quinolinones in high yields under neutral reaction conditions by a C À 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.
Transition-metal-catalyzedCÀSbondactivationforCÀCandC-heteroatom bond formation has fascinated organic chemists for decades.[1] A variety of organosulfur compounds have been utilized and have great potential in these processes [1][2][3] because of their ready availability, stability, and structural diversity, as compared to the corresponding organic halide coupling partners.[4] Cross-coupling chemistry with thioorganics along with new reaction patterns, exceptional selectivity, or unique reactivity would be highly desirable.Inspired by palladium-catalyzed desulfitative coupling of thioesters, [1c, 2a-d] we recently became interested in transitionmetal-catalyzed CÀS bond cleavage for CÀC bond formation during our research [5] on ketene dithioacetals, which are easily prepared and widely applied as organic intermediates.[6] We have already achieved copper-catalyzed desulfitative C À C cross-coupling of a-oxo ketene dithioacetals with arylboronic acids, [3a] and then palladium-catalyzed/copper-mediated desulfitative annulation of 2-methylthiobenzofurans with 2-hydroxyphenylboronic acids.[3b] More recently, a CÀS bond activation protocol for Heck-type cyclization of a-alkenoyl ketene dithioacetals was also developed in our group.[3c] To take advantage of the synthetic power of functionalized ketene dithioacetals [3,5,6] and the tremendous applications of arynes in cyclization reactions, [7] we envisioned the palladiumcatalyzed CÀS activation as the key to developing an annulation between arynes and a-carbamoyl ketene dithioacetals (1; Scheme 1) by the insertion of an aryne into a C À S bond. Furthermore, the expected products are 2-quinolinones (3) which have provoked great interest in chemical and biological fields.[8] However, the challenge of this strategy lies in avoiding the addition of the strongly nucleophilic sulfur atom in the substrates to the arynes (Scheme 1 A), and instead favoring insertion of the arynes into the CÀS bond. [9,10] To the best of our knowledge, transition-metal-catalyzed CÀS bond cleavage for aryne insertion has been seldom reported.[10]Herein, we report that arynes can react with ketene dithioacetals by palladium-catalyzed C À S bond activation followed by cyclization to produce 2-quinolinones, but they remain inactive towards the nucleophilic S-containing group (Scheme 1 B). The new synthetic method is also highlighted by the versatile transformations of the 4-functionalized 2-quinolinones, which are not easily obtained starting from the cor...
A novel catalytic alkylation of indoles with allylic alcohols has been developed. Catalyzed by sulfuric acid (10 mol-%), the reaction between indoles 2 and allylic alcohols 1 based on ketene dithioacetal affords polyfunctionalized indoles 3 in good to excellent yields with high regioselectivities under mild conditions. The catalytic carbon-carbon coupling reaction provides a facile method for the environmentally benign functionalization of indoles with the advantages of good regiochemistry, atom efficiency, easily available catalyst, good yields and the synthetic potential of the polyfunctionalized
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