Synthesis of 1-phenyl-3-methyl-1-butyne

[ibeza4]

aka: isopropylphenylacetylene

 

I have an idea how to get this, but it may be wrong or there may be an easier way to get to the product. The guidelines are: may only use benzene, acohols, alkyl halides with 3 carbons or less, and inorganic reagents can be used. I have a feeling there is an easier way since we don't even get into dehydrogenations and Sonogashira couplings in orgo2.

 

This is what I have:

1) Benzene + CH3CH2CL ->ALCL3-> to give ethylbenzene

2) dyhydrogenation performed to give ethenylbenzene

3) addition of Br2 to give (1,2-Dibromoethyl)-benzene

4) NaNH2 in lquid ammonia to give phenyl acetylene

5) Sonogashira Coupling performed with 2-bromopropane to give the final product

 

Thank you for any help that anyone can give.

[UC]

There is a reagent called trimethylsilyl acetylene, which has one end of a normal acetylene molecule protected from reaction. brominate the benzene, sonogashira with TMS-acetylene to TMS-ethynylbenzene, remove the TMS group (K2CO3 in methanol I believe), sonogashira #2 with iPrBr

[ibeza4]

Hmm that sounds like another possibility, but I can tell you we never covered that in class, or even the stuff I posted. I found the Sono coupling online. There must be a more basic way.

I do appreciate the response, UC.

[UC]

Perhaps a grignard reagent can be used to add the alkyl chain onto the benzene ring. If you converted the benzene ring into benzaldehyde, isobutylmagnesium bromide dehydration, bromination, and double dehydrohalogenation would yield the desired product.

 

Of course, you'd need to make the isobutyl bromide and benzaldehyde first, but it avoids the sonogashira.

[ibeza4]

Ah, good idea. I think this might be more of what the professor is looking for. I'll see what she thinks. Thank you very much