[reaction: see text] Stable oxapalladacycles have been prepared and converted into a series of highly functionalized 2H-1-benzopyrans via regioselective insertion of activated alkynes.

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[reaction: see text] Racemic homoallylic alcohols have been synthesized by palladium-catalyzed three-component coupling of an arylboronic acid, an allene, and an aldehyde.

Stable pallada(II)cycles L 2 Pd-1-C 6 H 5 -2-OCHCO 2 Et, featuring a Pd-bonded sp 3 -hybridized stereogenic carbon and bipyridine or bis(imine) auxiliary ligands (L-L), reacted with allyl bromides via a Pd(II)-Pd(IV)-mediated process involving a direct C(sp 2 )-H functionalization to afford highly substituted benzoxepines or benzopyrans. An allylpalladium(IV) complex, which was detected by low-temperature 1 H NMR analysis and characterized by X-ray crystallography, was shown to operate as an intermediate in the reaction sequence.

[reaction: see text] A chiral, nonracemic eta(3)-pyridinyl scaffold participates in [5 + 2] cycloaddition with electron-deficient alkenes, an allene, and an alkyne to give eta(3)-allylmolybdenum bicyclic adducts. The adducts can be demetalated, providing a convergent route to highly functionalized tropanes. High enantiocontrol can be achieved throughout the cycloaddition and demetalation sequence.