Which is the most efficient synthesis of (Z)-3-hexene from Alkyne?

Answer 1

The most efficient synthesis of (Z)-3-hexene from an alkyne is the hydroboration-oxidation reaction. Here's the stepwise process:

1. Start with an alkyne, such as 3-hexyne:

CH3CH2CH2C≡CH

2. Perform hydroboration by adding 1,2-dimethylborane (CH3)2BH and a suitable solvent, like tetrahydrofuran (THF). This reaction gives an anti-Markovnikov addition of BH2 to the alkyne, resulting in the formation of an intermediate alkene:

CH3CH2CH2CH=BH2

3. Next, perform oxidative workup to convert the boron group into a hydroxyl group. This is typically done by adding hydrogen peroxide (H2O2) and a base, such as sodium hydroxide (NaOH). The reaction conditions favor syn addition, giving predominantly (Z)-3-hexene:

CH3CH2CH2CH=CH2 + H2O2 + NaOH → CH3CH2CH2CH(OH)CH2OH

4. Finally, remove the extra hydroxyl group by using an acid, such as sulfuric acid (H2SO4), to give the desired product:

CH3CH2CH=CHCH2OH

Overall, this synthesis route efficiently converts the alkyne to (Z)-3-hexene using hydroboration-oxidation reactions.