| Popis: |
α-Acetylenic epoxides,R′CCCR″CH2 (1), have been converted into α-allenic alcohols, RR′CCCR″-CH2OH (3), by means of a palladium(0)-promoted reaction with R-ZnCl (2; R: Me3Si(C≡C)n-(n=1 or 2), H2CCH- or t-BuCHCCH-). Using this method, an improved synthesis of (±)-2,3-octadiene-5,7-diyn-1-ol, a metabolite from fungus Cortinellus berkeleyanus, has been developed. The method is not suited to the preparation of α-allenic alcohols from 1 and, for example, BuZnCl because of substantial formation of reduction products, HCR′CCR″-CH2OH. For the preparation of 3 from R = Me3SiC≡C other acetylides Me3SiC C-M were also studied, viz. M = Li, MgCl, Cu or Cu1/2Li1/2 but only with the cuprate could a reasonable conversion of 1 be realized. |
