As expected,[31 treatment of 4 with the primary 1,2-diarnines diaminomaleodinitrile, o-phenylenediamine, and 2,3-diarninonaphthalene gave the valenes 7 (50%, m.p. 209-210"C),["1 8 (95%, m.p. 122-125°C),"'.'31 and 9 (24%, rn.p. 209-2 11 oC)rl'l of quinoxaline-2,3-dicarbonitrile, phenazine, and benzo[b]phenazine, respectively. We also prepared analogues of 8 from 5 and 6.
Whereas the I3C N M R chemical shift of the bicyclobutane bridgehead carbon atoms (6= 10.0) of 4 is found in the normal region, the annelation of the pyrazine ring in 7, a quinoxaline unit in 8, and a benzoquinoxaline system in 9 to the tricyclo[3. 1.0.02.6]hexane framework leads, as expected,[I4] to considerable deshielding. The chemical shift values written above the formulas of 7-9 show an interesting tendency-namely, the deshielding decreases with increasing size of the aromatic system; on going from 7 to 9, A 6 = 12.9 ppm.
Experimental Procedure 4: Dimethyl sulfoxide (910 mg, 11.7 mmol) was added under NI over 3 min to a mixture of oxalyl chloride (1.27 g, 10.0 mmol) and dichloromethane (36 mL) cooled to -70°C. The resulting, stirred solution was treated within 5 rnin with 1 (500 mg, 4.46 mmol) in dichloromethane (9 mL) and then stirred for 40 min at -70°C. Subsequently, triethylamine (2.70 g, 26.7 mmol) was added to the milky mixture at this temperature. The mixture was stirred for an additional 5 min and then allowed to warm to 2 0 T , affording a colorless precipitate in a yellow to dirty green solution. Silica gel (3.0 g, 0.063-0.2 mm) was added, the resulting suspension was stirred for 5 min, and the dichloromethane was then carefully removed at 20 torr. The brown residue was placed on a column already containing 5.0 g of silica gel. After elution with tert-butyl methyl ether (ca. 180mL) until the column and the eluate were nearly colorless, the eluate was concentrated at 20 torr and dissolved in 3 mL of dry dichloromethane. Compound 4 was precipitated by addition of 4 mL of petroleum ether. Yield 179 mg (41%) yellow crystals, dec. 145-155°C (in a sealed tube).