# Synthesis of trans alkene with organoborane

Trans alkenes can be synthesized with organoboranes. The following sequence is represented in Smith's Organic Synthesis

How does the mechanism look like after the first step (hydroboration)?

I think this might be a alkyl shift that results in an $\mathrm{S}_{N}2$ type substitution at an $sp^{2}$ center. Cool. I've only ever seen $\mathrm{S}_{N}2$ type substitution at an $sp^{2}$ center for vinyl iodides. Unfortunately, I don't have my teaching materials on me at work, so I can't find the reference for this for you.
Note the "inversion" at the $sp^{2}$ center.
• Notice that even in that case, you need inversion of the $sp^2$ center. I am in fact proposing the exact same thing as you are. – Zhe Dec 16 '16 at 23:09