Reductive elimination with zinc copper couple

The second reaction which is akin to a -elimination involves reductive elimination of 2,2,2-trichloroethyl esters on treatment with zinc in acetic acid or zinc-copper couple in DMF to give Ll-dichloroethylene [Scheme LI l].19 The same... 

Different from the indirect reduction just mentioned (Scheme 45, substrate 178), chlorine in 7-position can frequently be eliminated by catalytic hydrogenation (palladium/charcoal) (96MI1), by zinc (02WOP64211) or by the zinc-copper couple in the presence of acetic acid (03MI3). The latter method even works with sulfur-containing chlorides when catalytic hydrogenation or zinc reduction failed for example, the 7-positioned chlorine of dichloride 181 is selectively removed (99JHC183). 

Conjugated polyene fragments occur in a wide variety of naturally occurring organic compounds, such as macrolides, carotenoids, and leukotrienes. The synthesis of all-trans triene 734 is readily accomplished by low-valent titanium-induced reductive elimination of l,6-dibenzoate-2,4-diene 733 [210] (Scheme 97). The requisite cis, c/5-diene geometry is obtained by a stereospecific reduction of diyne 731 with activated zinc—copper couple. 

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