[PoetryInMotion]

Problem. I am supposed to propose a way of synthesizing hex-4-ene-3-ol.

My thoughts. I am thinking about using a Grignard reagent and an aldehyde and follow one of the following routs:



I do, however, not recognizance the unsaturated Grignard reagent in the first route. Is it possible to synthesize it, and will it react like ordinary Grignard reagents?

Also, I am uncertain about whether the Grignard reagent will react directly to the aldehyde in the second route, or if it, perhaps, prefers an 1,4-addition. Free alkyl anions are, as far as I know, rather hard bases, which should favor the 1,2-addition. At the same time, I know that Gilman reagents prefer 1,4-addition, which makes me confused.

[opsomath]

Your first route is fine. 1-bromopropene will make a perfectly good Grignard reagent, it is easier to make vinyl Grignards than alkyl ones since the lone pair is in a sp2 orbital instead of an sp3.

[AlphaScent]

This is a good question and opsmath is correct in his answer.  The issue for me is practicality.  I synthesized a similar compound not to long ago and we decided on the second scheme.  The first chemically works just fine as opsmath said, but in practice it is cheaper and easier to buy Grignards.  Crotonaldehyde and ehtylmagnesium bromide are cheap.  Just a thought if its practical.  If you have to make the Grignard, then opsmath hit the proverbial nail on the head.

Cheers

[zsinger]

Buy the Grignards…..poor lab yields can be a problem for even intermediate organic lab rats such as myself (maybe 300 functional lab hrs.).  Add…..be happy………and voila…….the chemist has a desired product.  Be careful not to use too strong of an acid in the last step, as it can create NASTY byproducts.  Hope this helps.