Question

What reagents would I have to use to convert a trans alkene into a cis alkene?

example: trans-3-heptene to cis-3-heptene

My thoughts: I feel as if I would use Br2/CCl4 first to create a dihalide, then possibly 2NaNh2 and finally a lindlar catalyst to end with a cis isomer?

Answer 1

Make the epoxide of the trans alkene with McPBA. Open with tributyl phosphine. This will intercept the Wittig mechanism (after rotation of the C-C bond bewteen the carbons baring the oxygen and phosphonium), and you will lose the phosphine oxide and form the cis alkene.