Chemistry of Methyl 1‐Butyl‐Cyclopropene‐3‐Carboxylate: The Role of Transition Metal in Reaction Control: Rhodium‐Catalysed Synthesis of a Bicyclobutane, Coppercatalysed Dimerisation, Selective (Tl+++) Oxidation

Some typical reactions of a cyclopropenecarboxylate(I) were tentatively controlled by the use of transition metal catalysts. The reaction of (I) with methyl diazoacetate (DAM) afforded a dihydropyrazine(III) which was further dehydrogenated photochemically to the pyrazine(IV) whereas, the bicyclobutane(II) was obtained in the presence of rhodium acetate as catalyst. Copper triflate catalysed the ring opening of the cyclopropene ring and a dimer (the octatrienedicarboxylate(V) was thus isolated. Attempts to epoxidize(I) with a peracid (MCPBA) or V0(acac)2 and Mo0(acac)2‐t‐butyl hydroperoxide failed. Up to now, only thallium(III) nitrate afforded satisfactory selective oxidation of (I) (formation of the lactone VII). Copyright © 1986 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim