Cobaloxime anions (pyr(dmg)2Co-Na+) and/or hydrides (pyr(dmg)2CoH) react with cinnamoyl chloride and a variety of ynones and ynoates to produce cobaloxime-substituted α,β-unsaturated acyl complexes. The stereochemistry of the alkene produced by the ynone and ynoate hydrometalations can be controlled through choice of hydrometalation reaction conditions. Two of these new acyl complexes have been characterized by X-ray crystallography.

Reduced cobaloxime (cobaloxime ) [(pyridine)(dimethylglyoxime) 2 cobalt]) compounds react with a variety of oxygen-substituted allenic and propargyl electrophiles to produce cobaloxime-substituted R,β-or β,γ-unsaturated ketones and aldehydes. Two of the new unsaturated acyl complexes prepared have been characterized by X-ray crystallography. Several of the R,β-unsaturated acyl complexes were subsequently converted into 1-cobaloxime-1,3-dienyl complexes using Peterson or Petasis olefinations. One of these new dienyl complexes has also been characterized by X-ray crystallography.

Cobaloxime 1,3-dienyl complex, 2-pyridine bis(dimethylglyoximato)cobalt(III)−(3E)-1,3-pentadiene, participates in exo selective hetero Diels−Alder reactions with a variety of alkyl and aryl aldehydes. The cobaloxime-substituted cycloadduct products of these reactions can be demetalated to provide diastereomerically pure dihydropyrans with concomitant cobalt recovery. One of the cobaloxime-substituted dihydropyrans has been characterized by X-ray crystallography to prove the exo selective nature of the Diels−Alder cycloaddition.

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organic chemistry, review organic chemistry, review Z 0200 46 -299 Preparation and exo-Selective (4+2) Cycloaddition Reactions of Cobaloxime-Substituted 1,3-Dienes -(66 refs.). -(WELKER, M. E.; WRIGHT, M. W.; STOKES, H. L.; RICHARDSON, B. M.; ADAMS, T. A.; SMALLEY, T. L.; VAUGHN, S. P.; LOHR, G. J.; LIABLE-SANDS, L.; RHEINGOLD, A. L.; Adv.