convert the -SMe group to SO2Me using m-chloroperbenzoic acid and then heat the compound in any high boiling solvent it will be replaced

You may try the following method:

First oxidize the SMe group to SO2Me, then heat the compound with amine in sealed tube in DMF/DMSO solvent.

Once you succeed have the courtesy to tell us:) Thanks

Treat the Ar-SMe with m-CPBA in DCM for an hour, Check LCMS/Mass for Ar-SO2Me (sulfone), vac off the solvent; dissolve the residue in toluene, add 3eq DIPEA (base) and the amine, heat at 60°C for overnight. Job done. Good luck

John Boyd is right. The electron withdrawing effect will be greater if the cyano/nitro group is at a meta position in relation with the thioether group.

Another reagent capable of oxidizing the thioether group to a sulphone is the reagent known as Oxone (r).

The answer is yes, depending upon the aromatic group. If it is an electron-deficient heterocycle you can do it directly, although it would proceed better if the sulfur is oxidized to a sulfone. On benzene rings, direct displacement is problemmatical.

Dissolve/suspend SMe compound in amine (in the case of solid amine in glacial acetic acid + amine) and add an excess of 30 % hydrogen peroxide. In some cases is reaction exothermic and proceeds spontaneously.

There are all right. Just for example: I had methyl 4-(1-N-pyrrolyl)-2-(methylthio)pyrimidine-5-carboxylate and I had to replace SMe-group with different secondary amines. When I tried high temperature to replace directly, reaction goes very sluggish and I've got the mixture of SM, product and amide (carbmethoxy-group was also active). Releasing MeSH is also somehow problem because of smelling. But then after oxidizing MeS- to MeSO2- reaction with either secondary or primary amines goes smoothly and finished usually after 1h at 50'C in i-PrOH with high yields and no side-product formation.

Oxidation step was: DCM, 2,5 equivalent m-CPBA (slow addition), 0'C, 15 min. Water/sodium carbonate work-up.

very easy process just add equimolar ratio of the both compound and close it tightly in RBF for 3 to 4 day, then take the TLC, most of your reactant is convert in to tha product.

mCPBA, DMF/DCM. e.g. J. Med. Chem. 2012, 55, 3777−3791. then add amines.

I am completely agree with the suggestion of Prof. Boyd. In my opinion, the conversion of methylthio group to methylsulfonyl group is a good option. This methylsulfonyl group can be replaced by amines in sealed tube at high temperature.

Now the questioner has to reply :) whether he is succesful or still struggling

yep would be very interesting to know the outcome of this approach ... I bet it would be succesful :) ....

No, I repeated many times, the reaction is not going. Instead of SMe group, one of the ester group replaced.

Keep in mind though that depending on how electron rich the cycle is, you may get displacement of the sulfone with water or methanol if you use these solvents for the oxone oxidation for instance. It happened to me on a nitropyrimidine compound. Therefore I would stick to mCPBA (2.5 equiv) in DCM for the oxidation and then 20 equiv of the amine to displace the sulfone.