P,y-Ethylenehalides

Regio- and stereo-specific synthesis of alkoxy-3-ethylenes from 6-alkoxy-p,Y-ethylenehalides... 

Geospecific replacement. 1-Octyne and catecholborane stirred 2 hrs. at 70° under Ng, cooled to room temp., and stirred 2 hrs. at 25° with water -> frans-l-octenyl-boronic acid (Y 90%) dissolved in ether, cooled to 0°, aq. 3 N NaOH added followed at 0° by 20% excess iodine in ether with stirring, which is continued 0.5 hr. at 0° -> trans-l-ocitnyX iodide (Y 80%). Overall Y 71%. F. e. s. H. C. Brown, T. Hamaoka, and N. Ravindran, Am. Soc. 95, 5786 (1973) also cis-a,p-ethylenebromides with inversion of configuration s. ibid. 95, 6456 cis- and trans- ,/ -ethylenehalides via enesilanes cf. R. B. Miller and T. Reidienbadi, Tetrah. Let. 1974, 543. 

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