the following synth starts from para-dichlorobenzene which is brominated to 2-bromo 1,4 dichlorobenzene. this is used as is to do a grignard in ethyl ether to add the desired alkyl group. then the 2-alkyl 1,4 dichlorobenzene is heated to 300c with sodium hydroxide. benzyne rearrangement reaction will produce approximately 15% 3,5 dihydroxy alkyl benzene. catecholic isomers can be precipitated with lead acetate. hydroquinone isomers can be precipitated with h2s (sulfer heated with parrafin to 140c), not too much h2s or they will redissolve. unalkylated and polyalkylated resourcinols can be separated by distillation. alternate synth involves a separate step after bromination where the 2-bromo 1,4 dichlorobenzene is heated with anhydrous alcl3 to 140c for 8 hours to form the more thermodynamically stable 1-bromo 3,5 dichlorobenzene. then same as before except heating with sodium hydroxide in the presence of a copper catalyst at 140c to reduce benzyne reaction in favor of direct substitution.
