[girl101]

Hi , Can this reaction occur, I know I can form the enol, but I was wondering if an amide can also occur.
and can the enol tautomerize to form the keto or is it strictly from keto to enol. ( keto will be more stable right?)


Thank you for your assistance 

[spirochete]

Yes, but the mechanism you drew is definitely wrong. The amine is a pretty good nucleophile and the ketene is a good electrophile. The amine is not a strong enough acid to transfer a proton like that. Also there is a mistake in formal charges in your mechanism

[girl101]

I did a nu attack to from the enol .so are you saying the amide wont form?

a carbocation will form and i have nothing to neutralize it with. only reagents are ketene and amine.

[girl101]

figured it out thanks

[kriggy]

Yes it the reaction works. Its rather common if you use acyl chlorides for amide formations. Its one of the reasons, they are not used for peptide  bond formation because the ketene forms in some% and makes the chiral chloride racemize. It depends on the kind of base you are using AFAIK, (pyridine should be OK but TEA is strong enough to deprotonate the acyl chloride and form ketene. Or at least thats what Ive been told at class)

[hypervalent_iodine]

Yes it the reaction works. Its rather common if you use acyl chlorides for amide formations. Its one of the reasons, they are not used for peptide  bond formation because the ketene forms in some% and makes the chiral chloride racemize. It depends on the kind of base you are using AFAIK, (pyridine should be OK but TEA is strong enough to deprotonate the acyl chloride and form ketene. Or at least thats what Ive been told at class)

You are correct about TEA and strength of base, although it does work perfectly fine with TEA if the acyl chloride lacks α protons. You can avoid ketene formation through the use of anhydrous inorganic bases like K₃PO₄ (see Zhang et al., Tetrahedron Lett., 2009, 50, 2964-2966). It can take a bit longer, but the work up is much nicer than when you use amine bases, and you don't get racemization. I also imagine the addition of a PTC such as 18-crown-6 would help it along nicely, though I can't vouch for that. Personally, I've always used pyridine in these sorts of reactions with a CuSO₄ work up as racemization isn't an issue for me. Works a treat.