Cobalt-Catalyzed Synthesis of Alkenyl Heterocycles via Regioselective Intramolecular 1,4-Hydrofunctionalization of Dienes.

We report a novel cobalt-catalyzed intramolecular 1,4-hydrofunctionalization of dienes. The reaction proceeds under mild conditions and is amenable to N- and O-nucleophiles. The protocol exhibits exclusive regioselectivity, yielding a number of different alkenyl heterocycles, including but not limited to dihydroisobenzofurans, isochromanes, tetrahydrofurans, morpholines, lactones, and isoindolines. Experimental studies were performed to offer some insight into the different mechanistic pathways and to rationalize the regio- and stereoselectivities of the reaction.

Palladium-catalyzed ring-opening [5+2] annulation of vinylethylene carbonates (VECs) and C5-substituted Meldrum's acids: rapid synthesis of 7-membered lactones.

A novel approach for the synthesis of unsaturated 7-membered lactones by Pd-catalyzed [5+2] dipolar cycloaddition of vinylethylene carbonates (VECs) and C5-substituted Meldrum's acid derivatives has been developed. Various Meldrum's acid derivatives worked well in this reaction under mild reaction conditions. A variety of 7-membered lactones can be accessed in a facile manner in moderate to good yields by employing easily prepared Meldrum's acid derivatives.

Diastereoselective Synthesis of 1,2-Dihydrobenzofuro[3,2-b]pyridines via a Carbon-Carbon Double-Bond Cleavage/Rearrangement Cascade.

A new Lewis acid-catalyzed [2 + 2] cycloaddition/retroelectrocyclization (CA-RE)/1,6-addition relay of aurone-derived 1-azadienes and 1-alkynylnaphthalen-2-ols has been reported, leading to the regio- and diastereoselective synthesis of 1,2-dihydrobenzofuro[3,2-b]pyridine with a chiral carbon center and an axial chirality in good yields. This protocol enables the C-C double-bond scission/recombination to rapidly construct aza-heterocyclic architectures and features 100% atom utilization, a wide substrate scope, good compatibility with substituents, and excellent diastereoselectivity.

Electrochemical Annulation-Iodosulfonylation of 1,5-Enyne-containing para-Quinone Methides (p-QMs) to Access (E)-Spiroindenes.

A new electrochemical three-component annulation-iodosulfonylation of 1,5-enyne-containing para-quinone methides (p-QMs) has been established by using available arylsulfonyl hydrazides and potassium iodide under environmentally benign conditions. The electrosynthesis offers sustainable and efficient access to construct spirocyclohexadienone-containing (E)-indenes without any additional catalyst or oxidant through a sulfonyl-radical-triggered 1,6-addition and an I+-mediated ipso-cyclization cascade. Notably, potassium iodide plays the triple role of an electrolyte, a redox catalyst, as well as an iodination reagent.

Pd(II)-Catalyzed Carbonyl-Directing Activation of Alkenes: Selective Fluorosulfonylation and Aminosulfonylation of 1,7-Enynes.

A new Pd(II)-catalyzed carbonyl-directing activation of alkenes has been established, enabling radical-induced selective fluorosulfonylation and aminosulfonylation of carbonyl-tethered 1,7-enynes with sulfinic acids and N-fluorobenzenesulfonimide (NFSI) under mild and redox neutral conditions to access densely functionalized ( E)-3,4-dihydronaphthalen-1(2 H)-ones with generally good yields and high stereoselectivity. The selectivity of these bifunctionalizations relies on the electronic nature of substituents on both aryl rings of 1,7-enynes.