Increasing the Efficiency of the Transannular Diels–Alder Strategy via Palladium(II)-Catalyzed Macrocyclizations

Palladium(II)-catalyzed macrocyclizations of bis(vinylboronate ester) compounds are demonstrated to provide a strategically efficient approach to transannular Diels–Alder reaction substrates. In several systems reported, the macrocycle is preorganized such that cycloaddition at room temperature occurs concomitantly with cyclization. Numerous advantages over palladium(0)-catalyzed cross-coupling approaches are demonstrated

Cyclization Strategies to Polyenes Using Pd(II)-Catalyzed Couplings of Pinacol Vinylboronates

As a complement to Pd(0)-catalyzed cyclizations, seven Pd(II)-catalyzed cyclization strategies are reported. α,ω-Diynes are selectively hydroborated to bis(boronate esters), which cyclize under Pd(II)-catalysis producing a diverse array of small, medium, and macrocyclic polyenes with controlled <i>E,E</i>, <i>Z,Z</i>, or <i>E,Z</i> stereochemistry. Various functional groups are tolerated including aryl bromides, and applications are illustrated

Radical Isomerization and Cycloisomerization Initiated by H• Transfer

Under H₂ pressure, Co^II(dmgBF₂)₂L₂ (L = H₂O, THF) generates a low concentration of an H• donor. Transfer of the H• onto an olefin gives a radical that can either (1) transfer an H• back to the metal, generating an isomerized olefin, or (2) add intramolecularly to a double bond, generating a cyclized radical. Transfer of an H• back to the metal from the <i>cyclized</i> radical results in a cycloisomerization. Both outcomes are favored by the low concentration of the cobalt H• donor, whereas hydrogenation and cyclohydrogenation are more likely with other catalysts (when the concentration of the H• donor is high)

Cyclization Strategies to Polyenes Using Pd(II)-Catalyzed Couplings of Pinacol Vinylboronates

As a complement to Pd(0)-catalyzed cyclizations, seven Pd(II)-catalyzed cyclization strategies are reported. α,ω-Diynes are selectively hydroborated to bis(boronate esters), which cyclize under Pd(II)-catalysis producing a diverse array of small, medium, and macrocyclic polyenes with controlled <i>E,E</i>, <i>Z,Z</i>, or <i>E,Z</i> stereochemistry. Various functional groups are tolerated including aryl bromides, and applications are illustrated