Patent GB-953661-A (GB)
Title: Dibenzofuran derivatives
Inventor: MCCALL ERNEST BRYSON
IPC: C07D307/91
Filed: 1961-03-06
Abstract: The invention comprises 1,2-diphenyldibenzofuran and 1,4-diphenyldibenzofuran.  These compounds and, in general, dibenzofurans substituted by up to 4 aryl groups may be prepared by heating a hydrodibenzofuran, which is substituted by an aryl group or a radical that forms an aryl group on dehydrogenation, in the presence of a dehydrogenation catalyst or dehydrogenation agent.  The dibenzofuran may be part of a polycyclic benzeroid system as in naphthalene - the product then being, for example, an aryl-substituted benzonaphthofuran or an aryl-substituted dinaphthofuran.  The aryl group substituted in the dibenzfuran may be, for example, a phenyl or naphthyl group which may be substituted by a lower alkyl radical such as methyl, ethyl or isopropyl or by an aryl radical such as phenyl or tolyl.  In addition to the aryl group the dibenzofuran nucleus can carry an alkyl group or a halogen atom. Groups which may form an aryl group on dehydrogenation are, for example, cyclohexyl, cyclohexenyl or cyclohexadienyl groups which may carry hydrocarbon substituents as indicated above. Suitable dehydrogenation catalysts are, for example, platinum and palladium and dehydrogenation agents are sulphur and selenium.  The preferred temperature range for carrying out the process is 150-350 DEG C.  The hydrodibenzofuran starting materials may be obtained by reacting an oxo-hydrodibenzofuran with a Grignard agent R1MgX, where R1 is an aryl or hydroaryl group and X is a halogen atom, preferably in a solvent, and decomposing the resulting organo-magnesium complex.  In the examples (a) 1-oxo-octahydrodibenzofuran in ethereal solution is reacted with phenyl magnesium bromide and the product is treated with water to give a mixture of 1-phenyl-3, 4, 6, 7, 8, 9-hexahydrodibenzofuran with a little 1-phenyl-1-hydroxy-octahydrodibenzofuran which is heated with palladium on carbon to give 1-phenyldibenzofuran; (b) a mixture of 2-chlorocyclohexanone, sodium o-phenylphenate and o-phenylphenol is heated to give 2(21-phenylphenoxy) cyclohexanone which is treated with phosphorus pentoxide and phosphoric acid to give 4-phenyl-6, 7, 8, 9-tetrahydrodibenzofuran which is then dehydrogenated by heating with selenium to give 4-phenyldibenzofuran; (c) 2-chlorocyclohexanone is heated with an aqueous solution of 4-phenylcyclohexan-1, 3-dione and potassium hydroxide and the resulting mixture treated with sodium hydroxide to give a mixture of 1-oxo-2-phenyl-and 1-oxo-4-phenyl-octahydrodibenzofuran; the 1-oxo-4-phenyl compound is separated and treated with phenyl magnesium bromide and the product treated with hydrochloric acid, the 1,4-diphenyl-3, 4, 6, 7, 8, 9-hexahydrodibenzofuran so formed is then dehydrogenated with palladium on carbon to give 1,4-diphenyldibenzofuran; if the mixture of 1-oxo-2-phenyl- and 1-oxo-4-phenyl-octahydrodibenzofuran is treated in a similar way a mixture of 1,2-diphenyl and 1,4-diphenyl-dibenzofura is obtained, and (d) 1-oxo-4-phenyloctahydrodibenzofuran is heated with sodium in diethyleneglycol; the mixture is then acidified and 4-phenyloctahydrodibenzofuran is separated and dehydrogenated to give 4-phenyldibenzofuran.