cf. CA 50, 6383b. Various 9-methylphenyl- and 9-dimethylphenyl-1,2-benzanthracenes (I) were prepd. and catalytically cyclodehydrogenated to give II. 9-(p-Tolyl)-1,2-benzanthracene (III) (1.0 g.) in 60 ml. dry C6H6 heated 2 hrs. on a steam bath with 6 g. anhyd. AlCl3, the cooled mixt. decompd. with 100 ml. 10% HCl, and the aq. layer extd. 5 times with 25 ml. C6H6, the washed and dried C6H6 evapd. and the oily residue chromatographed from 5 ml. C6H6 on Al2O3, eluted with petr. ether 1 week and the remaining yellow band eluted with 500 ml. C6H6, and the fraction triturated with 20 drops EtOAc yielded 17% yellow solid, m. 208-9 Deg, recrystd. from C6H6-alc. to give II (R = 2'-Me, R' = H), m. 210-11 Deg, unchanged on sublimation. Other cyclodehydrogenations with AlCl3 similarly carried out gave low yields of II (R, R', % yield, and m.p. given): 4'-Me, H (III), 19, 206-7 Deg; 3-Me' (or 1'Me), H (IV), 13, 213-14 Deg; 2'-Me, H (V), 17, 210-11 Deg; 4'-Me, 3'-Me, 23, 201-2 Deg; 4'-Me, 2'-Me, 2, 198-9 Deg; 4'Me, 1'-Me, 3, 207-9 Deg; 3'-Me, 1'-Me, 2, 215-16. A rather large variety of reagents and reaction conditions was tried in an attempt to improve the yields without success, including AlCl3 in boiling CS2, AlCl3 in boiling p-cymene, fused AlCl3-NaCl, anhyd. FeCl3, SnCl4, AlCl3-SnCl4, and POCl3 all in boiling C6H6, Pd-C at 350 Deg, Pd-C in boiling p-cymene, and S at 325 Deg/5 mm. II gave brilliant yellow-green fluorescent solns. and the claret soln. in concd. H2SO4 changed to olive-green in 1 min. II (R = R' = H) (X) and III, IV, and V gave picrates, m. 231-2, 226-7, 220-1, and 217-18 Deg, resp. The ultraviolet and visible spectra were measured at 5 mg./ l. and 10 mg./l., resp., in alc. and the tabulated data showed the characteristic bathochromic shift of alkyl derivs. of polynuclear aromatic hydrocarbons. Carcinogenic activity tests showed V to be a potent carcinogen.