ADDITION OF PYRUVATOXIMES TO EXOCYCLIC DOUBLE-BONDS

This communication reports on the obtainment of 2-[2-(4-methyl-3-cyclohexenyl)]-oximinopropanoic acid on addition of methyl or ethyl pyruvatoximes to limonene in the presence of catalysts consisting of Pd supported on SiO2/AlPO4. As a rule, oximes can be readily prepared from hydroxylamine hydrochloride and a carbonyl compound. They are highly versatile and allow the synthesis of a variety of products by rearrangement,1,2 oxidation3 and reduction.4 Oximes can be reduced either with dihydrogen over supported metal catalysts5 or by hydrogen transfer,6 which yield the corresponding amine as main product. The oxime of pyruvic acid yields alanine on reduction. The reaction involving dihydrogen is very well known. The literature also includes references to the reduction of oximes by hydrogen transfer over Pd/C catalysts using cyclohexene or cyclohexadiene as hydrogen donor.7 However, the reduction of hydroaromatic compounds such as limonene does not yield the expected results in terms of regioselectivity or alanine as the main reaction product.