[acarter5251]

Hi,

I have been trying to troubleshoot a reaction, and am currently having a difficult time. 

I am trying to have phenylmagnesium bromide add to a benzonitrile derivative to yield the corresponding benzophenone.  Each time I perform the reaction, I see multiple products being formed, and they are the same each time I do the reaction.  I have also attempted making the tertiary alcohol by having the PhMgBr add to a corresponding aldehyde, and I see the same products being formed.

This led me to believe that the issue lie in my Grignard reagent or the conditions used for the reaction.  I tried subjecting just the Grignard to the same conditions, but with no substrate, and I see the same products being formed.  Quenching the Grignard in acid gives me one product being formed.  Therefore, I have come to the conclusion that it must be the reaction conditions rather than my reagent.

Is it possible that the Grignard is reacting with the air to give me these other products?  I thought that the volatility of the ether would give me a protective blanket over the reaction, but it is the only possibility that I can think of.

Are there any suggestions on how I can overcome this issue with my reaction?

[TheUnassuming]

What other functional groups do you have on your molecule that contains the nitrile/aldehyde?  Addition into nitriles can be a little finicky, but aldehydes are usually fairly clean.

What temp are you doing this at?  It sounds like you are doing it in an open flask?  It might be good to give us a more detailed description of what you are doing.

[acarter5251]

What other functional groups do you have on your molecule that contains the nitrile/aldehyde?  Addition into nitriles can be a little finicky, but aldehydes are usually fairly clean.

What temp are you doing this at?  It sounds like you are doing it in an open flask?  It might be good to give us a more detailed description of what you are doing.

There is a methoxy and a hydroxyl that has been protected with tert-butyldimethylsilyl chloride.  I am conducting the reaction on a small scale in a vial with the cap closed.  I have tried the reaction at 0 Celsius as well as at room temperature.

[TheUnassuming]

Since you are working on small scale, it will take very little exposure to water/air to make things go badly (especially if its a little humid outside).  Use a 5mL flask or the like so you can put a septum in it, or engineer a septum on the top of your vial, but find a way to put the reaction under inert atmosphere which will help.  Where is your solvent coming from/source?

Is your hydroxyl ortho to your aldehyde/nitrile by chance?

Have you characterized any of the products from the reaction?

[acarter5251]

Since you are working on small scale, it will take very little exposure to water/air to make things go badly (especially if its a little humid outside).  Use a 5mL flask or the like so you can put a septum in it, or engineer a septum on the top of your vial, but find a way to put the reaction under inert atmosphere which will help.  Where is your solvent coming from/source?

Is your hydroxyl ortho to your aldehyde/nitrile by chance?

Have you characterized any of the products from the reaction?

Okay, I will give that a try.  The hydroxyl is not ortho, and I haven't characterized the products from the reaction.  I just know that the crude NMR does not show my expected product.

[TheUnassuming]

Yeah, more data is good.  If you can find out what you are making, it will be easier to troubleshoot the reaction.

I asked about an ortho- O-Si protecting group because it can very easily migrate in strongly basic conditions in that position.