[Dee]

I'm trying to synthesize α-amino-phosphonates using different aromatic aldehydes and 2-amino quinoline and diethyl phosphite as a catalyst. The problem is i'm not getting yield more than 20 percent.

Any suggestions ?

[discodermolide]

If you want α-amino-phosphonates why are you using diethyl phosphite as a catalyst? Should it not be there in equal amounts (molar)?

[Dee]

If you want α-amino-phosphonates why are you using diethyl phosphite as a catalyst? Should it not be there in equal amounts (molar)?

Thanks for your time and suggestion, after the formation of imminium ion ( from aromatic aldehyde lets say benzaldehyde and 2-aminoquinoline) I'm using diethyl phosphite to make alpha amino phosphonate..

[discodermolide]

Yes, I realise that but why are you only using catalytic amounts as you said in your first post.
You should be using molar equivalent amounts of diethyl phosphite  not catalytic.

[orgopete]

How are you removing the water? Is 20% the fraction of imine you actually form and all of it reacts?

[Dean]

I did that last year. That's called Kabachnik reaction. You can learn more about it from Wikipedia.
I think catalytic acid would improve the reaction.

[discodermolide]

The whole point is that the OP needs to be using molar equivalents of phosphite.

[Dee]

Yes, I realise that but why are you only using catalytic amounts as you said in your first post.
You should be using molar equivalent amounts of diethyl phosphite  not catalytic.

Yeah in my earlier trials i used only catalytic amount of diethyl phosphite. I tried today with equivalent amount after reading your post, i used only catalytic amount because of the steric factors of the bulkier imminum ion from quinoline. I'll check the spectra tomorrow.
Thanks alot, I hope It might work

[Dee]

How are you removing the water? Is 20% the fraction of imine you actually form and all of it reacts?

yes good point, i didn't use any dehydrating agents as such, I was just separating my product using ternary separation, from the aqueous layer. I'll use phosphorus pentachloride in the next set up. nope I'm getting 20% of the whole alpha amino phosphonate. i guess the there is some problem in the formation of Imminium ion only thats why the yield is low.
Thanks though ..

[Dee]

I did that last year. That's called Kabachnik reaction. You can learn more about it from Wikipedia.
I think catalytic acid would improve the reaction.

Yes it is based on Kabachnik field reactions, thanks for the suggestion