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A series of dihydropyrans bearing a dicobalthexacarbonyl moiety have been found to undergo an efficient Al-promoted O → C ring-contraction process. This rearrangement reaction operates successfully for a broad range of substrates. Moreover, the potential of this approach for generating cyclopropanes from the corresponding dihydrofurans has been demonstrated.

The reaction of γ-amino-α,β-unsaturated esters prepared from l -serine with diversely substituted arylcuprates affords the corresponding syn -adducts. Transformation of the amino group to an isocyanate, followed by Friedel–Crafts intramolecular condensation, leads to enantiopure 3,4-disubstituted tetrahydroisoquinolin-1-ones, which can be reduced to the corresponding tetrahydroisoquinolines.