I would like to aminoalkylate an aryl compound with aldehyde, and pyridine by Mannich reaction.
The HCl was not used as catalyst since it is preferable to obtain a secondary amine product instead of an amine salt product.
Hence, a basic DMAP catalyst was used.
Both DMAP and pyridine consist of a secondary amine group. Is it possible that the Mannich reaction carried out with the DMAP instead of the desired pyridine?
Yes, DMAP can be used as catalyst in addition u can also try DBU & TMG.
Neither 4-Dimethylaminopyridine (DMAP) nor pyridine "which is aromatic compound" consist of a secondary amine group. In fact, the 4-dimethylamino part in DMAP contains a tertiary amine.
In principle, Mannich reaction is condensation of a non-enolizable aldehyde, an amine and an enolizable carbonyl compound which yields an amino methylated product. Mannich reaction is a nucleophilic reaction.
If a) the reaction does not occur under acidic condition and if b) ammonia or primary or secondary amines are NOT used, then we cannot expect a positive outcome. So please change your reactants to be in line with the requirements of Mannich reaction.
I've never seen DMAP used for a Mannich reaction - which is not to say that it won't work. It's much more basic, and much more nucleophilic, than pyridine, and it may catalyze unwanted side reactions. Whether it works or not depends very much on the structures of the three components that you're trying to condense. Try it and see, is the only advice I can give!
You could also try Lewis acids, if you need to avoid HCl:
https://kundoc.com/download/cecl37h2o-as-an-efficient-catalyst-for-one-pot-synthesis-of-amino-ketones-by-thr_5a91d719d64ab2212b9fd2c8.html
Mannich reaction requieres a secondary amine, which dimethylaminopyridine is not.
The Mannich Reaction is a reaction between ammonia, a primary or secondary amine often as the hydrochloride salt, formaldehyde, and a compound with an activated hydrogen. ( see e.g. FF Blicke Org React 1, 303-341, a review of the Mannich reaction). As an acid or acid equivalent is required, addition of a strong tert base such as DMAP to the reaction mixture serves no purpose. However, the product, as the amine salt, may be neutralized after workup, either with a strong base or a suitable basic resin.
I fail to see what the desired reaction product is from the information provided in the question. I am not aware that pyridine will act as the amine component under Mannich conditions and I will welcome a reference that describes this use as well as a reference for direct aminoalkylation of an aryl ring under the same conditions. Assumptions are like weeds in a garden.
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