Birch reduction of alkynes

Scheme 69. Birch reduction of alkynes to trans-alkenes.

The stereochemistry of the vinyl sulfone does not matter because it is immediately reduced by an electron from sodium to give a vinyl radical. Much as you saw above, in the Birch reduction of alkynes, the vinyl radical collects a second electron and becomes a vinyl anion, which chooses to adopt the more stable configuration before being protonated to give the predominantly alkene. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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