Chemistry of Dicyclopropylcarbene and Related Intermediates in Dimethyl Sulfoxide

Article abstract of DOI:10.1021/jo00296a010

The potassium salts of the anions of (phenylsulfonyl)hydrazones of diisopropyl, isopropyl cyclopropyl, and dicyclopropyl ketone were decomposed in dimethyl sulfoxide in the temperature range of 110-130 deg C.The diisopropyl phenylsulfonyl anion decomposes to form 2,4-dimethyl-2-pentene and diisopropyl ketone.Similar decomposition of the isopropyl cyclopropyl substrate forms 1-cyclopropyl-2-methylpropene, 1-isopropylcyclobutene, and isopropyl cyclopropyl ketone, while thermal decomposition of the dicyclopropyl ketone (phenylsulfonyl)-hydrazone anion forms cyclopropylcyclobutene and dicyclopropyl ketone.The rate constants for the first and second steps of the consecutive first-order decomposition of the (phenylsulfonyl)hydrazone anions were determined over the temperature range of 110-130 deg C.The activation parameters ΔH* (kcal/mol), ΔS* (eu), and ΔG* (kcal/mol) were calculated for the diazo compound to carbene step (k2) for the diisopropyl (15.6 +/- 1.1, -30.9 +/- 2.8, and 27.7 +/- 1.6), the isopropyl cyclopropyl (27.7 +/- 2.0, 3.3 +/- 5.1, and 26.4 +/- 2.8), and the dicyclopropyl (36.8 +/- 1.8, 28.4 +/- 4.6, 25.6 +/- 2.5).These results are discussed in terms of two factors: interaction of the cyclopropane ring with the functional group and orientation of the polar solvent.