[chungfaitao]

How do you synthesize 1-methyl,3-nitrobenzene starting from methylbenzene?

I've pasted my method below. I'm not sure if it would work, and I guess there is probably a simpler way. Any help would be appreciated.

[AnkurGel]

After preparing 3-nitro benzoic acid, you can always increase the chain of carboxylic acid by adding methyl group by 'Arndt-Eistert reaction'[http://en.wikipedia.org/wiki/Arndt%E2%80%93Eistert_reaction] {It's a single step reaction} . Then you can decarboxylate the chain to give methyl group as the final substituent in lieu of carboxylic acid; which gives the desired product.

[SVXX]

Actually you add a methylene group, Ankur. It's a homologation of the present carboxylic acid R-COOH to R-CH₂-COOH.
For more info on mechanism and such - http://www.organic-chemistry.org/namedreactions/arndt-eistert-synthesis.shtm.
Hence after the preparation of 3-nitrobenzoic acid, the following steps would be required -:
1. Reaction with PX₅ to form acid halide.
2. Reaction of acid halide with diazomethane or CH₂N₂ to form a diazoketone.
3. Subsequent Wolff rearrangement of the diazoketone into a ketene.
4. At this point, different nucleophiles when added to the mixture can influence the path to different products. An alcohol will give you an ester, an amine will give you an amide and water will give you the homologue acid.
5. Perform decarboxylation of this to get the desired product.

[chungfaitao]

Would it work to decarboxylate the 3-nitrobenzoic acid, and then perform a Friedel-Crafts reaction to put the methyl group back on? In other words, would the Friedel-Crafts reaction put the methyl group into the correct position?

[SVXX]

Friedel Crafts reactions don't work on nitrobenzenes. EAS reactions like further nitration do work, but FC reactions don't. The nitro group present deactivates the substrate to a level beyond FC participation.

[chungfaitao]

OK, suppose I go the Arndt-Eistert synthesis route. Can I just decarboxylate the product with NaOH then?

[orgopete]

Stick with your original route or plan to nitrate, reduce, acylate, nitrate, hydrolyze, diazotize, and reductive cleavage of diazonium salt to your final product. That is the common route in many textbooks.

[SVXX]

orgopete I would've suggested diazotization but he wanted a shorter route.
And you decarboxylate with NaOH/CaO, not just NaOH, chung.