Stereoselective double addition of chiral alkynyl-zincs to cobalt-stabilized acetylenedicarbaldehyde

Acetylenedicarbaldehyde, a desirable but intractable C4 synthon, can be protected as the Gorgues’ dicobalt hexacarbonyl complex. It undergoes chimio-, diastereo- and enantioselective attack of terminal alkynes using zinc triflate and (−)-N-methyl-ephedrine to afford stable complexes of chiral secondary carbinol-skipped oligoynes.