How can 2-indanone be prepared?
If you need to start with ortho-xylene, then you should use fazekazs's approach. I searched through SciFinder and found that the most commonly reported synthesis of 2-indanone involves oxidation of indene using a variety of conditions. 

The following Organic Synthesis prep highlights this approach, although it certainly uses some outdated methodology (distillation by aspirator vs. rotary evaporation, for example). Newer reports use a variety of oxidations, including oxone or the the Wacker process.

In this example, indene 1 is added to a mixture of formic acid and hydrogen peroxide to afford the monoformate ester of indene 1,2-diol 2. The monoformate ester was hydrolyze with sulfuric acid to give 2-indanone 3.

 

However, when I first saw your question, I wanted to propose a synthesis based on a Dieckmann condensation on diethyl phenylene-1,2-diacetate 4 followed by decarboxylation of the $\beta$-ketoester 5. However, I did not find this approach in the literature, and both the diacetate ester and its parent diacid are of comparaple price to 2-indanone. 



Another interesting idea that I did not find in the literature is a pericyclic approach based on photolysis or thermolysis of beznocyclobutene 5 in the presence of carbon monoxide. Following electrocyclic ring opening, intermediate 6 can react with CO in 4+1 cycloaddition. An isocyanide could be used instead of CO, and hydrolysis of the imine would give 2-indanone. Alternatively, there may be a transition metal species that could mediate this transformation.