Small but effective:: Copper hydride catalyzed synthesis of α-hydroxyallenes

(Chemical Equation Presented) Mild and efficient: The copper hydride catalyzed diastereoselective SN2′ reduction of propargyl oxiranes provides α-hydroxyallenes bearing various functional groups (ethers, esters, alcohols; see scheme, PMHS = polymethylhydridosiloxane). The best results were obtained with a copper hydride catalyst and an N-heterocyclic carbene ligand. The resulting allenes are useful substrates, as they undergo, for example, regio- and chemoselective cycloisomerization to give 2,5-dihydrofurans. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.