Stereoselective synthesis of fully substituted ethylenes via an Ag-catalyzed 1,6-nucleophilic addition/annulation cascade

Synthesis of Chromenopyrroles (Azacoumestans) from Functionalized Enones and Alkyl Isocyanoacetates

Elegant synthetic strategies for chromenopyrroles (azacoumestans) have been devised via cycloaddition of 2-hydroxychalcone/cyclic enones and alkyl isocyanoacetate, followed by lactonization. Herein, ethyl isocyanoacetate acts as a C-NH-C-C═O synthon contrary to its hitherto applications as a C-NH-C synthon. Subsequently, pentacyclic-fused pyrroles were also constructed from the o-iodo benzoyl chromenopyrroles using the Pd(II) catalyst.

Rhodium-Catalyzed C-H Annulation of Free Anilines with Vinylene Carbonate as a Bifunctional Synthon

Chemical transformation with vinylene carbonate as an emerging synthetic unit has recently attracted considerable attention. This report is a novel conversion pattern with vinylene carbonate, in which such a vibrant reagent unprecedentedly acts as a difunctional coupling partner to complete the C-H annulation of free anilines. From commercially available substrates, this protocol leads to the rapid construction of synthetically versatile 2-methylquinoline derivatives (43 examples) with excellent functionality tolerance.

An efficient domino strategy for synthesis of 3-substituted 4-oxo-4,5-dihydro-1H-pyrrolo[3,2-c]pyridine derivatives in water

A strategy for catalyst-free domino reaction of 4-aminopyridin-2(1H)-ones, arylglyoxal hydrates and different 1,3-dicarbonyl compounds in water has been established. The mild and efficient procedure afforded pyrrolo[3,2-c]pyridine derivatives with 76-94% yields after simple crystallization. The present procedure shows promising characteristics, such as readily available starting materials, the use of water as reaction media, simple and efficient one-pot operation, and avoiding the need for any hazardous or expensive catalysts.

Engaging yne-allenones in tunable catalytic silane-mediated conjugate transfer reductions

New tunable catalytic [2+2] cycloaddition/silane-mediated conjugate transfer reductions of yne-allenones have been developed, by which substituent-diverse cyclobutarenes with generally good yields were selectively synthesized by adjusting Fe-H and Cu-H catalytic systems. Use of the Fe-H system triggers 1,6-conjugate reduction to dihydrocyclobuta[a]naphthalen-4-ols whereas the Cu-H complex enables 1,4-conjugate reduction to cyclobuta[a]naphthalen-4(2H)-ones.

Enantio- and Regioselective CuH-Catalyzed Conjugate Reduction of Yne-Allenones

A new asymmetric catalytic conjugate reduction of yne-allenones to synthesize enantioenriched cyclobuta[a]naphthalen-4(2H)-ones has been established that uses copper-bisphosphine complexes as catalysts and gives excellent regio- and enantioselectivities (≥99% ee) in most cases. This protocol tolerates a broad scope of substrates, exhibits high compatibility with various substituents, and gives excellent stereoselectivity, providing a catalytic and efficient entry to fabrication of synthetically important chiral 6-6-4 tricarbocyclic scaffolds.