I do not know if it is really feasible to synthesize. I found the link that says attempted trial failed. I think this compound will be very hard to isolate even if you synthesize it

https://archive.org/stream/synthesisofcerta00book/synthesisofcerta00book_djvu.txt

Dicyanoacetylene was of interest not only as a possible pi

complexing reagent but also as a possible starting material in

the synthesis of hexacyanobenzene , a compound unreported in the

literature, which should also be of interest as a pi acid. Diels

and Alder-"-^ obtained hexamethyl mellitate in 25 per cent yield

from the addition of pyridine to dimethyl acetylenedicarboxylate

in acetic acid. Analogous trimerizations were attempted with

dicyanoacetylene; (1) by addition to a solution of acetic acid

and pyridine, (2) passage of the vapor into a solution of acetic

acid and pyridine and (3) in^to a solution of benzene, acetic

acid and pyridine, and (4) addition of a solution of acetic acid

and pyridine to a solution of dicyanoacetylene in benzene.

catalyst

NCCSCGN > C6(CN)6

Recent research in pi complexations with tetracyanoethylene

and other low molecular weight unsaturated compounds indicates

that other unsaturated alkyl nitriles and polycyanobenzenes

might be expected to demonstrate pi complexation ability. Few

compounds of this nature have been previously studied.

The pi complexing ability and ultraviolet absorption spectrum

of dicyanoacetylene was studied. The dicyanoacetylene did not

display any tendency to undergo pi complexation, either as a pi

acid with naphthalene, or as a pi base with bromine and tri-

nitrobenzene . Upon extended contact with bromine, however, an

addition compound, C4N2Br2, was formed which had not previously

been isolated. The attempt to trimerize dicyanoacetylene to form

hexacyanobenzene yielded no positive results.

The feasibility of applying the Friedman modification of the

Rosenmund-Von Braun method of nitrile synthesis from halogens

was investigated briefly. 1,2,4, 5-tetrachlorobenzene failed to

react under a variety of conditions in the attempt to find an

alternate synthesis for the recently reported 1 , 2 , 4, 5-tetracyano-

benzene .

The pilot work in the preparation of a series of fully sub-

stituted polycyanobenzenes is described. The 3 , 6-positions of

1, 2 , 4, 5-tetramethylbenzene (durene) were readily brominated under

mild conditions with good yields. However, oxidation of the

methyl groups to the corresponding 3 , 6-dibromopyromell itic acid

I also found that this compound is commercially available. There is also CAS number. Check it out. 

http://www.lookchem.com/NewSell/memberproductdetail.aspx?spid=6289718#.VvcXafl942w

Surprising part is reaction of C6F6 with Me3SiCN didn't produce any C6(CN)6.

I think the nature of sterics and electronics won`t allow that kind of transformation..

Vendors and synthesis routes for C6(CN)6 :

http://www.molbase.com/en/synthesis_1217-44-3-moldata-1714846.html#tabs

@Hamidreza Samouei : ..C6F6 with Me3SiCN didn't produce...add catalytic F- ( (Me2N)3S+Me3SiF2-, Bu4N+F- and so on) - it should help. Me3Si-CN do not produce ionic cyanide for nucleophilic attack, it can  isomerise reversible  in isocyanide form only

Thank you,

Surprisingly adding catalytic amount of TBAF or TBACN to mixture didn't help.

Dear Hamidreza, could you provide experimental procedure? The idea is to compare with published data from US 7592486 . As reported, TBACN react with C6F6 during 1h at room temperature in acetonitrile. Strickly anhydrous conditions was applied as C6(CN)6 is very sensitive to nucleophils.

Hexachlorobenzene is cheap precursor for C6F6 preparation in reaction with KF and it  is maybe better for hexacyanobenzene synthesis

Dear Andrei,

So many thanks,

Unfortunately, this patent and original paper(J. AM. CHEM. SOC. 2005, 127, 2050) is full of errors and their claims are totally wrong.

In light of this info from you - what product is in sell from C6(CN)6 vendors? :-)

If problem is really actual, l think about direct synthesis from C6Cl6 + KCN + 18-Crown-6 in autoclave conditions (but in glass ampule - to avoid possible reaction to phthalocyanine compounds).

C6Br6 + CuCN is also promising combination, in N-methylpyrrolidone or pyridine/quinoline ( http://www.orgsyn.org/demo.aspx?prep=CV3P0631 ) . Materials are available by reasonable price from http://store.molbase.com/product-29170.html , http://store.molbase.com/product-20644.html

Classical synthesis of C6F6 from C6Cl6  + KF need ~500oC, but in presence of (Et2N)4P+Br- as PTC  reaction proceed at much lower temperature.