I am to turn 1-octyne to 1-hexene.
1) Reduction using sodium metal in pure ammonia to an alkene.
2) Halohydrin formation; the -OH installs at the more substituted carbon due to its greater ability to stabilize positive charge (this always confused me; the more substituted carbon is both more positive in character and has more electron-donating methyl groups?)
3) Conversion of OH to a good leaving group (-OTs) using a sulfonate ester and a weak base, pyridine.
4) E2 elimination using NaOH and heat. Because of resonance and sheer bulk and negative induction the OTs(-) should make for a better leaving group than Br-. So the internal alkene is formed.
5) Two-part one step ozonolysis; creation of aldehyde.
6) Reduction of carbonyl with hydrogen and transition metal to terminal alcohol.
7) Conversion of terminal alcohol to a better leaving group using tosyl chloride and pyridine again.
8) Use of LDA to deprotonate and create the terminal alkene.
Also we can take another route with the brominated alkene; we can use OsO4 and basic hydrogen peroxide to create a 1,2 (vic) diol, which can be cleaved by periodic acid, and this creates a primary alcohol, which we convert to a good leaving group using tosyl chloride and pyridine, and we can eliminate. Same number of steps, but just something different that I thought of. Well, perhaps slightly simpler since there isn't a need for a two-step process (ozonolysis).