enter image description here

I'm trying to design a synthesis of D from C. All I can think of is using $\ce{Me2CuLi}$ to add the methyl group to the alkene. I thought maybe then if isobutyl bromide was in the reaction mixture when $\ce{Me2CuLi}$ pushed the negative charge onto the oxygen and it came back down that could do an $\mathrm{S_N2}$ with isobutyl bromide, but I've never seen that before. Then for converting the carbonyl to an alkene I have no idea.

  • 3
    $\begingroup$ The Wittig reaction may be useful. $\endgroup$ – bon May 6 '16 at 18:35
  • $\begingroup$ Ah of course, the Wittig reaction with $H_3C-^+PPh_3$ as the phosphonium salt? Just the dialkylation I'm not sure about now. $\endgroup$ – draksi May 6 '16 at 18:57
  • $\begingroup$ I was thinking of Baylis-Hillman to add the isobutyl group, but I don’t think that works well enough with alkyl halides =C $\endgroup$ – Jan May 6 '16 at 19:34

You are right about using the Gilman in a 1,4-Michael addition. The enolate created from this can then be used in the nucleophilic attack of a haloalkane. Then all that's left to do is a Wittig reaction, swapping the carbonyl oxygen for a carbon. The full stepwise synthesis would be:

enter image description here

| improve this answer | |
  • 1
    $\begingroup$ Could also use Tebbe/Petasis methylenation $\endgroup$ – SendersReagent May 8 '16 at 2:56
  • $\begingroup$ Alkylation of the enolate with isobutyl bromide will likely give substantial elimination. 3-Bromo-2-methylprop-1-ene will be more reactive and not undergo elimination. Reduce the double bond with Pd/C/H2. Alternatively, trap the enolate with isobutyraldehyde, dehydrate with acid and hydrogenate. $\endgroup$ – user55119 Mar 4 '18 at 3:52

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.