The first examples of highly diastereoselective tandem 8/9-endo-dig and 8-exo-dig hydroalkoxylation-formal-[4 + 2] cycloaddition are described for the synthesis of medium ring heterocycle-fused chromenes.

A substrate dependent regio‐ and stereoselective domino hydroalkoxylation‐formal‐[4+2] cycloaddition is described for the facile synthesis of linear as well as spirocyclic 1,4‐heterocycle‐fused chromene ketals. Enantiospecific synthesis of oxazepino chromene derivatives was successfully carried out using chiral pool amino alkynols. The developed hydroalkoxylation cascade offered rapid access to the spirocyclic [6‐6‐7‐6] tetracyclic core of cytorhizhins B–D with correct relative configuration.

A protocol involving intramolecular formal [4 + 2]-cycloaddition of in situ generated o-azaquinone methide for the facile synthesis of 1,4heterocycle-fused quinoline motifs is demonstrated. The cascade involved tandem CÀ O, CÀ C, and CÀ N bond formation and also exhibited excellent functional group tolerance. Enantiomerically enriched 1,4-oxazepino quinolines were synthesized using alkynols derived from L-amino acids. The sulfoxide embedded quinolines were transformed to pentacyclic 1,4-thiepino tethered indeno-quinoline scaffolds via Pummerer cyclization.

TMSOTf mediated reaction of alkynyl vinylogous carbonates serendipitously gave 1,4-oxazepine and dihydropyran dienes via transposition of ethyl acrylate moiety involving intramolecular cascade Prins type cyclization/retro-oxa-Michael reaction/cycloisomerisation. The developed atom-economical protocol...

Designed CoNi bimetallic catalysts on various supports were synthesized and tested for selective hydrogenation reactions. Amongst these, the newly developed CoNi@gC3N4 nanocatalyst demonstrated a unique reactivity profile. It was found to be most effective for selective hydrogenation of various chalcone derivatives and nitroarenes in the presence of other reducible functional groups such as halo, carbonyl, benzyl ether, cyclopropane, and isolated alkenes. The prepared bimetallic catalyst has advantages over the reported methods in terms of catalytic activity under mild conditions, selectivity, and reusability. The catalyst CoNi@gC3N4 has ability to selectively reduce nitro functional group to amine and allows formation of quinolines.