[sharbeldam]

Can grignard reaction contain a double bond it's chain? or does it have to be alkyl.

Grignard reagents are RMgX, but is the R always alkyl or can it contain double bonds/triple bonds/halogens?

[rolnor]

Double bonds are OK. What do you think about halogens, can Grignards react with alkylhalides? Terminal tripple bonds, what about the acidic hydrogen, could that be a problem?

[sharbeldam]

So grignard are strong bases, they can react with the acidic hydrogen of triple bonds, and halogens i guess can react via sn2 with it.

But im glad my reaction above works! thank you!!

[rolnor]

You are welcome!

[Babcock_Hall]

In the presence of an alkyl halide, I wonder whether or not a Grignard might exchange into a different Grignard.  I am just speculating.

[rolnor]

I dont think so, alkyllithium can do this but not grignard.

[hollytara]

You can buy vinyl magnesium halides and allyl magnesium halides from places like Sigma-Aldrich so definitely double bonds and Grignards can coexist!

[rolnor]

The butenyl-Grignard you have in the scheme is also commercially available.

[Babcock_Hall]

I dont think so, alkyllithium can do this but not grignard.

To my surprise there appears to be a synthetically useful exchange reaction:  https://onlinelibrary.wiley.com/doi/full/10.1002/anie.200300579

[rolnor]

Yes, I recall this now, I can not read the full paper. Maybe even terminal acetylene would be possible? I think you use a Grignard together with LiCl?

[Babcock_Hall]

I just skimmed the article.  In some cases, aryl bromides or iodides are converted into aryl MgCl. I did not see LiCl in the exchange step itself, but I did see it in the next step, along with CuCN, in some syntheses. 

[rolnor]

The structure looks OK but is the name wrong, should it not be 4-butenylmagnesiumbromide?

https://www.acros.com/portal/alias__Rainbow/lang__en/tabID__34/DesktopDefault.aspx