[Cacoethes]

How can I turn butane into CH₂=CH-CH=CH₂?  Can I just use light and Br₂ to make Br-CH2-CH2-CH2-CH2-Br and then tert butox to make double bonds?

[nj_bartel]

Well, you're going to selectively halogenate at the more substituted (secondary) position, due to radical stability, so what you end up with after radical bromination is CH₃-CHBr-CHBr-CH₃.  The problem you run into with treating this with a strong base is that if you use a moderately strong base, you're only going to get one elimination (to the more substituted alkenyl bromide) then be stuck.  I think you might be safe using a strong, hindered base like LDA, but not entirely sure.

[azmanam]

hindered base necessary for hoffmann product