Palladium-Catalyzed Cyclization of Alkynoic Acids To Form Vinyl Dioxanones Bearing a Quaternary Allylic Carbon

Pd/Brønsted Acid-Catalyzed Atom-Economical [3 + 3] Annulation of 4-Hydroxycoumarins and Skipped Enynes

We report an unprecedented application of skipped enynes as bis-electrophiles under palladium/Brønsted acid catalysis. A [3 + 3] annulation of skipped enynes with 4-hydroxy coumarins as bis-nucleophiles enables a completely atom-economic synthesis of fused O-heterocycles. The reaction is proposed to proceed via the Pd-catalyzed C-H activation of the skipped enyne leading to a diene, which upon subsequent activation by Pd and an O-nucleophilic attack leads to the regioselective formation of a six-membered heterocyclic ring, with a vinyl substituent.

Pd/Brønsted acid catalysed intramolecular N-allylation of indoles and pyrroles with alkynes for the synthesis of N-fused heterocycles

We, herein, report a Pd(0) and Brønsted acid-catalyzed redox-neutral intramolecular N-allylation of indoles and pyrroles with alkynes for the synthesis of biologically important imidazolidinone-fused N-heterocycles. The allylation is completely atom-economical and is applicable to a wide range of substrates. The methodology eliminates the use of a leaving group or an oxidizing agent, often employed for the allylation of nucleophiles. To the best of our knowledge, N-allylation of indoles and pyrroles with alkynes has not been reported to date.

Synthesis of tricyclic oxazinoindolones via Pd-catalyzed intramolecular addition of carboxylic acids to alkynes

A completely atom-economical synthesis of the oxazinoindolone core via the Pd-catalyzed intramolecular addition of carboxylic acids to alkynes has been developed. Oxazinoindolones have been known to have varied biological activities. The reaction proceeds via 6-exo-dig cyclization and affords the products in high yields (55-93%). The developed method demonstrates the applicability of a Pd(0) complex in combination with a substrate-tethered acid for the 1,2-addition of carboxylic acids to alkynes.

Site-selective synthesis of 1,3-dioxin-3-ones via a gold(i) catalyzed cascade reaction

A novel gold(i)-catalyzed protocol for the synthesis of 4H-1,3-dioxin-3-ones is presented.

Construction of N-Heterocyclic Systems Containing a Fully Substituted Allylic Carbon by Palladium/Phosphine Catalysis

The unique cyclization of benzamide derivatives that contain an alkyne by a Pd(0)/dialkyl(biaryl)phosphine catalytic system is reported. The reaction efficiently provides a variety of six-membered N-heterocyclic compounds that contain a fully substituted carbon center without the need for a stoichiometric additive. Mechanistic studies suggest that this unprecedented cyclization starts with the cleavage of a propargylic C-O bond, and a 1,3-diene has been identified as a relevant intermediate.

Organocatalytic sulfa-Michael/aldol cascade: constructing functionalized 2,5-dihydrothiophenes bearing a quaternary carbon stereocenter

A practical sulfa-Michael/aldol cascade reaction of 1,4-dithiane-2,5-diol and α-aryl-β-nitroacrylates has been developed, which allows efficient access to functionalized 2,5-dihydrothiophenes bearing a quaternary carbon stereocenter in moderate to good yields with high enantioselectivities.

Highly efficient synthesis of benzodioxins with a 2-site quaternary carbon structure by secondary amine-catalyzed dual Michael cascade reactions

Employing salicylic acids and substituted 3-butyn-2-ones as the substrates, a morpholine catalyzed tandem dual Michael addition afforded a benzodioxin skeleton.