[hsvilenov]

can give me an idea how can i synthesize 1-metyl 3-nitro benzen(m-nitro toluen)

[HP]

Good question
In direct nitration toluen you'll obtain only o- and p-nitro toluenes because the resonance forms..
m-nitro toluene may be synthesized indirectly from p-toluidine(p-NH2 toluene which obtained from reduction of p-nitro toluene with Zn/HCl ). para-toluidine is then acetylated with acetic anhydride to the coresponding acetylated base which further with HNO3 is nitrated on m-position of CH3 group. After that with NaOH you;ll hydrolyze the amide to the free NH2 group obtaining p-amino m-nitro toluene. This intermediate in diazotation reaction with NaNO2+HCl giving diazonium N2Cl salt which is reduced(liberating N2) with stanium chloride in alkaline media(Mayer) to the desired m-nitro toluene  

[o alquimista]

Here is HP his post as a chemical equation.

[HP]

Quite a precise scheme alquimista ths!

[o alquimista]

Some extra information: Both -NH2 and -NHCOR are o,p-directors. However in a reaction mixture containing a Lewis acid such as H2SO4, HNO3, or AlCl3 the amino group becomes a m-directing, deactivating NH3+ group.

[o alquimista]

Maybe its possible to do it the other way around; first the nitro group and then the CH3.

Nitrate benzene, or start with nitrobenzene an m-director.

Then use methane iodide and a catalyst. Thing is you can't use a smaller halogen then I. Because smaller methylhalogens have a BP below room temperature and are very carcinogenic (not a fun combination ). And does CH3I with AlCl3 or another catalyst work?

If not then reaction with HCOCl + AlCl3, or para-formaldehyde, followed by a reduction might work. Although reaction with para-formaldehyde can (as I have once synthesized after discovering it as a by-product of a chloromethylation reaction) also give a bis-aromatic product Ar/\O/\O/\Ar.

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PS: This hole post might be nonsense, but I am just wondering whether a shorter reaction route is possible.

Also if you were to synthesize a bigger alkyl group than methyl, the nitro group first method would definetely be easier and arguably better than starting from the alkyl-aromatic.  

Another point I would like to make with this post is that in synthesis problems creativity is of crucial importance.

[HP]

Aha if nitrobenzene is m-director then with Br2/FeCl3 you'll obtain m-bromo nitrobenzene. Then CH3I/Mg/ether as  Grignard reacent reaction will lead to m-nitro toluene i guess...

[movies]

Grignard reagents sometimes add to nitro groups.  Check out the Bartoli Indole Synthesis.

[HP]

Interesting synthetic route for indole synthesis using Grignard, movies. May be with m-nitro bromobenzene it wouldnt work the same but using the highly reactive MeMgI make some doubts for some kind chemical interactions with NO2 group i guess. May be similar as shown in detail mechanism in Bartoli synthesis. But also the classical reaction Grignards with Ar-X will take place most and the final product predominanetly be the desired Really interesting to be checked this route if alredy no one had done it in lab...