ALKYLATION AND OXIDATIONS OF SYMMETRICAL DIMETHYLENEBIPHENYL AND RELATED DIANIONS (CYCLOPHANE, BIPHENYLOPHANE, NMR, CONFORMATION).

Abstract

Bis-benzyl dianions were prepared from the three symmetrical dimethylbiphenyls in yields of 79-86%, and shown to react with a variety of electrophiles on the benzylic carbons. Electrophiles included dimethyl and diethyl sulfate, isopropyl bromide, t-butyl iodide, allyl chloride, trimethylsilyl chloride, trimethylgermyl bromide, and trimethyltin chloride. Reaction of the dianions with (alpha),(omega)-dihalides provides an excellent route to n.0 - and n.0.n.0 cyclophanes. An X-ray study on 14.0 paracyclophane showed it to have a conformation different from that observed in solution by NMR; MM2 calculations were used in determining what the solution conformation is likely to be. Oxidation of the dianions produced the monomer dihydrophenanthrene from the ortho isomer, dimer 2.0.2.0 metacyclophane from the meta isomer, and polymer from the para isomer. An X-ray study on 2.0.2.0 metacyclophane showed it to have the same conformation in the crystal as is observed in solution by NMR. An NMR method for determining the angle of twist in a biphenyl based on the chemical shift of the ortho hydrogens was developed. Many oxidizing agents were evaluated for the oxidation of the dianion from 2,3-dimethyl-1,3-butadiene to 1,2,5,6-tetramethylenecyclooctane; cupric bromide was found to be the best.