We can do by using base but i think it will not go because formation of stable anion: chance of O-alkylation as well as N-alkylation.

Would a base like cesium carbonate be ok for you? on another hand have you thought at doing your synthesis the other way around, I mean: using diphenyl amine + the required acid chloride. Good luck.

Have also a look at :

http://www.organic-chemistry.org/synthesis/C1N/amines/amines.shtm

Might give you some extra ideas

Dear Laurent F Bornaghi, using acid chloride  i can do but i have so many primary amide already in stock so i want from that. I checked your given link but there primary amine to amide conversion is given.

You have answered your question already. If you use a base, you will get both N- and O-alkylation. If you do not use a base, your amide is not nucleophilic enough in order to be selectively alkylated. I would go with secondary amine and acid chloride

But i want selectivity any how.

Try a mild base (cesium carbonate or similar) in a two phase system with a phase transfer catalyst.

You can try Buchwald-Hartwig cross coupling for those. To couple amide, CuI is the most widely used catalyst system for coupling amides. You can start with the conditions found in Buchwald JACS 2002, 7421.

http://pubs.acs.org/doi/pdf/10.1021/ja0260465

wihtout base u can use methyl iodide.you can also use formaldheyde and formic acid in DMSO.

You can alkylate N-aryl primary amides in refluxing toluene using powdered KOH as the base. In our case, it works in high yields using primary mesylates as alkylating agents, starting from N-aryl acetamides. Easy and cheap. Benzyl bromide should work fine.

If you want to make an N-aryl bond, this is another story. You need to perform a transition-metal coupling reaction, as indicated by Pierre-André Fournier.

I forgot to say that you must use a catalytic amount of nBu4NHSO4 (phase-transfer catalyst) in your alkylation reactions. So 1.0 equiv of amide, 1.0 to 1.5 equiv of alkylating reagent, 2.0 equiv of powdered KOH, 5% equiv nBu4NHSO4 in refluxing toluene.

N-arylation of amides:   T. Ikawa, T. E. Barder, M. R. Biscoe, S. L. Buchwald, J. Am. Chem. Soc., 129:13001-13007 (2007).