[shafaifer]

Greetings,

My problem is:

56. Starting with ethyne, describe how the following compounds could be synthesized:
a. (3S,4R)-4-bromo-3-hexanol and (3R,4S)-4-bromo-3-hexanol
b. (3R,4R)-4-bromo-3-hexanol and (3S,4S)-4-bromo-3-hexanol

My thinking is:

Firstly, I would react ethyne with two times (NaNH₂ and CH₃CH₂Br) in order to synthesise the desired amounts of C-C bonds.

The next step in the synthesis would be to have a reaction of the newly formed alkyne with HBr in which bromine will attach to either of the sp-carbons and hydrogen to the other. This alkene would then have to undergo a reaction with: 1. BH₃/THF an 2. HO^-, H₂O₂ and water - this destroys the double bond and OH is bonded to carbon number 3. I am not sure if this proposal can justify the production of any of the requested compounds - I hope it can. What could I do with the structures that this method does not account for - or if my method is totally useless - what could I do?

[orgopete]

I agree with forming the hexyne.

Hint: the products may be formed from bromine/water (plus some additional step(s)).

[shafaifer]

Yes, thank you very much, I see now that the step beforehand is either H2 and NH3(l) or H2 and lindlar catalyst.