Diels-Alder additions of dicyanoacetylene to aromatic hydrocarbons

✍ Scribed by Engelbert Ciganek

• Publisher: Elsevier Science
• Year: 1967
• Tongue: French
• Weight: 233 KB
• Volume: 8
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)89880-4

✦ Synopsis

Only a few examples of Diels-Alder additions to monocyclic aromatic hydrocarbons are known so far. Benzyne (1) and hexaf .o-2-butyne (2) add to benzene, and the adducts of hexafluoro-2-butyne (2) at;,. dicyanoacetylene (3) to durene have been prepared. We have found that 2,3-dlcyanoblcyclo[2.2.2locta-2,5,7-triene (1) is formed In 14% yield when a solution of dlcyanoacetylene In benzene is heated to 1.80" for two days, and that the reaction is strongly accelerated by aluminum chloride. In the presence of this Lewis acid, the addition proceeded at room temperature to furnish compound ; In 63% yield in addltlon to the Friedel-Crafts products phenylmaleonitrile (4%) and phenylfumaronitrile (11%). 2,3-Mcyanoblcyclo[2.2.2locta-2,5,7-triene (i), m.p. + NC-C =C-CN -CN + '@;>C=CHCN I CN N MeCN U2-U3", Amax 315 mu (E 830) and 232 mu (E 5700), was identified by Its nmr spectrum (In CDC13), which showed multiplets at T 3.1 (4H) and T 4.9 (2H), and by catalytic hydrogenation to a tetrahydro derivative, 2,3-d1cyanoblcyclo-[2.2.2]oct-2-ene (2_), which was identical with the hydrogenation product of the adduct 2 (3) of dicyanoacetylene and 1,3-cyclohexadiene.