No abstract

Regio-as well as stereo-specific reductions of a wide variety of acetylenic derivatives have been carried out in absolute ethanol with zinc powder activated with 1 ,2-dibromoethaner and with zinc powder activated successively with dibromoethane and copper(1) bromide, the first reagent being less powerful and more selective than the second one.

A Quick Procedure for the Partial Reduction of Triple Bonds.-Various acetylenic compounds are partially reduced to give the corresponding olefins using zinc activated by the addition of either 1,2-dibromoethane or 1,2-dibromoethane and lithium bromocuprate. Whereas the latter reagent system is more powerful, the former proves to be more selective. Some examples of application are outlined in the reaction scheme. The yields achieved reach in general values above 90 percent. -(AERSSENS, M. H. P. J.; VAN DER HEIDEN, R.; HEUS, M.; BRANDSMA, L.; Synth. Commun. 20 (1990) 22, 3421-3425; Dep. Prep. Org. Chem., Debye Res. Inst., Utrecht Univ., NL-3584 CH Utrecht, Neth.; EN)

Durch Reduktion der Diacetylene (II) mit Zinkpulver, das durch 1,2‐Dibromethan (I) aktiviert wird, entstehen die Enine (III).