The synthesis and rearrangement of methyl 2,2,4,4-Tetramethylbicyclo[1,1,0]-butane-1-carboxylate

Abstract

The title compound (4) was prepared by the intramolecular alkylation of methyl 3-tosyloxy-2,2,4,4-tetramethylcyclobutane-1-carboxylate (3). Compound (3) was prepared by two different routes.     Heating compound (4) in the vapour phase at c. 150° gave three products isomeric with (4). Two of these products, methyl trans-3- isopropenyl-2,2-dimethyl-cyclopropane-1-carboxylate and methyl 2- isopropenyl-4-methylpent-3-enoate, were shown to be products of an acid-catalysed rearrangement; the third product, methyl 2- isopropylidene-4-methylpent-3-enoate, was shown to be the true product of pyrolysis.