2 EFFICIENT ROUTES TO M-TERPHENYLS FROM 1,3-DICHLOROBENZENES

In the first route 2,6-dichlorophenyllithium (5), prepared by direct l ithiation of 1,3-dichlorobenzene, reacted with aryl Grignard reagents to give m-terphenyls in 57-93 % yields(Table 1); the methodology was e xtended to substituted 1,3-dichlorobenzenes (i.e. 8 --> 10). Also, rea ction of 5 with MgCl2 gave 2,6-dichlorophenyl-magnesium chloride which , on warming, produced the self-capture product tetrachloro-m-terpheny l 7 in moderate yield. In the second route, reaction of 1,3-dichlorobe nzene with excess of aryllithium in diethyl ether at room temperature gave the corresponding m-terphenyls in 59-94% yields (Table 2). Exampl es are given in which the aryllithium was prepared by three different routes (ArX + Li, ArX + t-BuLi, ArH + BuLi).