Two Syntheses of [2.2.2] (1,2,3)Cyclophane

Two syntheses are presented for 2.2.2] (1,2,3)cyclophane (7), the remaining member of the symmetrical 2_n]cyclophanes whose preparation has not previously been described. The first method involved the dimerization of 2,6-bis (4′, 4′-dimethyl-2′-oxazolinyl)toluene ( 1 ) to give 2 which, on hydrolysis, produced the tetracarboxylic acid 3 . Conversion of 3 , via the acid chloride ( 4 ), to the tetraol 5 , followed by treatment with phosphorus tribromide yielded the tetrabromide 6 . The overall scheme was then completed by reaction of 6 with phenyllithium to give 2.2.2] (1,2,3) cyclophane ( 7 ). An alternate, more convenient, method began with the pyrolysis of 2,6-bis (chloromethyl)toluene ( 8 ) to give 3-chloromethylbenzocyclobutene ( 9 ). Formation of the Grignard of 9, followed by reaction with ferric chloride, yielded the dimer 10 . Pyrolysis of 10 then gave 2.2.2] (1,2,3)cyclophane (7).