- Cyclopropane formation by nickel-catalysed electroreductive coupling of activated olefins and unactivated gem-dibromo compounds
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Cyclopropyl derivatives have been prepared with good yields by transition-metal catalysed electroreductive coupling of activated olefins and unactivated gem-dibromo compounds. This electrolysis is characterized by the use of a Fe/Ni catalyst system, acetonitrile as the solvent and a catalytic amount of triphenylphosphine as ligand. This procedure is a good alternative to the classical preparations of cyclopropyl derivatives from activated olefins (Simmons-Smith reaction, 1,3-dipolar addition of diazomethane, 1,4-addition of phosphorus and sulfur ylides).
- Sengmany, Stéphane,Léonel, Eric,Paugam, Jean Paul,Nédélec, Jean-Yves
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p. 271 - 277
(2007/10/03)
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- Coordination Catalysis in Organic Electrosynthesis. Stoichiometry and Products of Reduction of Dibromomethane by Ni(0) Complexes with π-Acceptor Ligands
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Reaction of Ni(0) complexes with dibromomethane gives different final products depending on the nature of the process in the stage of oxidative addition, which proceeds either through the elimination of two bromide ions to give intermediate carbene, or by the elimination of one bromide ion, depending on the ligand enviroment in the metal complex.
- Budnikova,Petrukhina,Kargin
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p. 257 - 259
(2007/10/03)
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- Synthesis of Cyclopropyl Carbocyclic Nucleosides
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As representatives of a novel class of carboxylic nucleoside analogues (+/-)-cis-, (-)-cis and (+/-)-trans 9-(2-hydroxymethylcyclopropyl)-adenine (= -methanol) were synthesized from the corresponding dialkyl 1,2-cyclopropane dicarboxylates.
- Csuk, Rene,Scholz, Yvonne von
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p. 10431 - 10442
(2007/10/02)
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- Stereoselective 1,3-debromination reactions
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The metallate, PPN(1+)Cr(CO)4NO(1-), was used for the 1,3-debrominative reductive cyclization of the (+/-) and meso isomers of dimethyl 2,4-dibromoglutarate and dimethyl 2,4-dibromo-2,4-dimethylglutarate.In both (+/-) isomers, the reaction is stereospecific in giving the trans cyclopropane product.In the meso case, the reaction is unselective in the first case, but distinctly favors the cis cyclopropane isomer in the second set of compounds.This (+/-) and meso pair thus represent the first example of near stereospecifity in the debromination of both 1,3-dibromo diasteromers.Using an enantiomerically enriched dimethyl 2,4-dibromo glutarate, and determining the absolute stereochemistry of the cyclopropane product, it was found that a strict double inversion () mechanism is involved in the (+/-) debromination reaction and presumably also in the near-stereospecific meso case reported above.
- Liu, Yingchun,Sorensen, Ted S.,Sun, Fang
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p. 258 - 262
(2007/10/02)
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- Synthesis of Dimethyl 1,2-Cycloalkanedicarboxylates by Electrochemical Cyclization of Dimethyl α,α-Dibromoalkanedioates Using a Copper Anode
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The electrochemical cyclization of dimethyl α,α'-dibromoalkanedioates by making use of a platinum cathode and a copper anode in the presence of sodium iodide gave three- to six-membered dimethyl 1,2-cycloalkanedicarboxylates in good yields.
- Tokuda, Masao,Hayashi, Atsushi,Suginome, Hiroshi
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p. 2590 - 2592
(2007/10/02)
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- Facile Synthesis of Racemic 3-Acetoxy-2,6-dimethyl-1,5-heptadiene, the Sex Pheromone of the Comstock Mealybug
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A three step synthesis of 3-acetoxy-2,6-dimethyl-1,5-heptadiene is described.Starting from methyl chloroacetate and methyl acrylate, trans- and cis-dimethyl 1,2-cyclopropanedicarboxylate have been prepared.The isomers were treated with methyllithium or methylmagnesium iodide to give the corresponding diols in high yields.Heating the trans diol in a mixture of acetic acid and acetic anhydride at 80 deg C gave the title compound in an overall yield of 50percent based on methyl chloroacetate.The corresponding cis diol gave, under the same conditions, 2,2,4,4-tetramethyl-3-oxabicyclohexane as the only product.
- Skatteboel, Lars,Stenstroem, Yngve
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- Cyclopropanediamines, 3. - Pure Diastereomers of 1,2-Cyclopropanedicarboxylic Acids and Derivatives
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Efficient preparations of pure diastereomers of dimethyl 1,2-cyclopropanedicarboxylates 2, dicarboxylic acids 3, dicarbonyl dichlorides 4, and dihydrazides 5 are reported.Mixtures of diastereomers of dimethyl dicarboxylates 2a, b, d, e are obtained from α,β-unsaturated methyl carboxylates 7 and methyl α-chlorocarboxylates 8 as well as from 7c, d and the sulfur ylide 10 (2c, d).The diastereomers are separated by fractionating distillations (2a, b, c, e) or crystallization (2d) on a 100-g to 1-kg scale (d.e. >99percent).Only low yields of 2c are obtained in the reaction of methyl crotonate (7c) with methyl α-chloroacetate (8a), since 7c predominantly dimerizes to afford 12.The diesters 2 are converted into the pure diastereomeric diacids 3, dicarbonyl dichlorides 4, and dihydrazides 5. 3,3-Dimethyl-cis-1,2-cyclopropanedicarboxylic acid (cis-3f) is obtained by trans-->cis isomerization of trans-3f with the help of acetic anhydride and sodium acetate as catalyst.The configurations of 2-6 and 12 are confirmed by 1H NMR spectroscopy.Derivatives of cis-1,2-dimethyl-1,2-cyclopropanedicarboxylic acid tend to form bicyclic products.Thus, the reaction of cis-3e with phosphorus pentachloride yields mainly the cyclic anhydride 6e and only small amounts of the dicarbonyl dichloride cis-4e.Furthermore, the dihydrazide cis-5e slowly cyclizes in the solid state to give the N-aminoimide 13 and hydrazine, a reaction which is fast in solution.Pure 13 is obtained by thermolysis of cis-5e at 60-65 deg C under high vacuum.
- Saal, Wolfgang von der,Reinhardt, Robert,Seidenspinner, Hubert-Matthias,Stawitz, Josef,Quast, Helmut
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p. 703 - 712
(2007/10/02)
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- CYCLOPROPANATION OF DIMETHYL FUMARATE AND MALEATE WITH GEM-DIHALIDES CATALYZED BY Co(0)- OR Ni(0)-COMPLEX AND ZINC.
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The reaction of bis(acetonitrile)bis(diethyl fumarate)cobalt(0) with dibromomethane gave diethyl trans-1,2-cyclopropanedicarboxylate in a 67% yield based on the cobalt complex. Dimethyl cis-1,2-cyclopropanedicarboxylate was obtained in a 52% yield from the reaction of dimethyl maleate with dibromomethane in the presence of acetonitrilebis(dimethyl maleate)nickel(0) accompanied by the formation of the trans-isomer in a 14% yield. The addition of zinc gave cyclopropanes in over 100% yields based on cobalt or nickel. 3-Methyl- and 3,3-dimethyl-1,2-cyclopropanedicarboxylic acid esters were produced by the reaction of dimethyl fumarate or maleate with 1,1-dibromoethane and 2,2-dibromopropane. The yield in the cobalt catalyst system decreases with an increase of substituents of gem-dibromides, while that in the nickel catalyst system does not vary appreciably.
- Kanai,Nishiguchi,Matsuda
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p. 1592 - 1597
(2007/10/02)
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- Enzymes in Organic Synthesis. 24. Preparations of Enantiomerically Pure Chiral Lactones via Stereospecific Horse Liver Alcohol Dehydrogenase Catalyzed Oxidations of Monocyclic Meso Diols
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Preparative-scale horse liver alcohol dehydrogenase catalyzed oxidation of monocyclic meso diols provides a direct and convenient one-step route to a broad range of chiral γ-lactones of value as synthons in asymmetric synthesis.The general applicability of the method is demonstrated by oxidations of cis-1,2-bis(hydroxymethyl) substrates of the cyclohexyl, cyclohexenyl, cyclopentyl, cyclobutyl, cyclopropyl, and dimethylcyclopropyl series.For each diol, oxidation of the hydroxymethyl group attached to the S chiral center occurs exclusively, and the pure γ-lactone products are isolated in high (68-90percent) yields and of 100percent ee.In contrast, the enzyme does not exhibit significant enantiomeric selectivity in its catalysis of oxidations of the corresponding racemic trans diols.The stereospecificities observed, or lack thereof, are as predicted by the active-site model.
- Jakovac, Ignac J.,Goodbrand, H. Bruce,Lok, Kar P.,Jones, J. Bryan
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p. 4659 - 4665
(2007/10/02)
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