Ring Opening Of Methylenecyclopropanes Research Articles

Ring opening of methylenecyclopropanes with halides in liquid sulfur dioxide

Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewis acid properties that solubilizes inorganic salts. The unique properties of SO2 were demonstrated by control experiments: 1) upon performing the reactions with the aforementioned salts in conventional solvents, the MCP ring opening was not observed either in the presence of catalytic amounts of H3PO4 (similar pKa to that of H2SO3), or in the absence of H3PO4; 2) a solution of SO2 in THF exhibited similar properties to that of liquid SO2.

ChemInform Abstract: Synthesis of Fluorinated Homoallylic Compounds by Fluoroalkyl Radical Mediated Ring Opening of Methylenecyclopropanes.

ChemInform Abstract: Synthesis of Fluorinated Homoallylic Compounds by Fluoroalkyl Radical Mediated Ring Opening of Methylenecyclopropanes.

Brønsted acid-mediated ring-opening reactions of methylenecyclopropanes: a dramatic counter ion effect

We report herein two different ring-opening patterns of methylenecyclopropanes (MCPs) in the presence of two Brønsted acids heptadecafluorooctane-1-sulfonic acid (C 8F 17SO 3H) and toluene p-sulfonic acid (TsOH) under mild conditions: (a) the ring-opening of MCPs by H 2O and subsequent etherification give the corresponding homoallylic ethers in the presence of heptadecafluorooctane-1-sulfonic acid; (b) the direct ring-opening of MCPs by the Brønsted acid gives the corresponding homoallylic alcohol derivatives in the presence of toluene p-sulfonic acid.

Density functional study of the insertion and ring-opening mechanism of MCP over Cp2LaH and Cp2LuH catalysts.

The insertion and ring opening of methylenecyclopropane (MCP) catalyzed by Cp2LnH (Ln = La and Lu) was investigated using DFT method. Geometries and energies of the reactants, minima, and transition states for this reaction were obtained. The present study indicates the formation of Cp2LaH-MCP complex followed by 1,2-insertion through a tetrahedral transition state with subsequent ring opening at the proximal bond via hydrogen transfer transition state resulting in the formation of the final product.

Ring Opening of Methylenecyclopropane over Lanthanocene Catalyst: A Quantum-Chemical Molecular Dynamics Simulation Study

The ring opening of methylenecyclopropane (MCP) catalyzed by lanthanocene (Cp 2 LaH) was simulated using a novel tight-binding quantum-chemical molecular dynamics method under reaction temperature. The results indicate theformation of the Cp 2 LaH-MCP complex by 1,2-insertion with a subsequent hydrogen transfer followed by the ring opening of the proximal bond.

Inter- and intramolecular palladium-catalyzed hydrocarbonation of methylenecyclopropanes with carbon pronucleophiles

The inter- and intramolecular additions of pronucleophiles to methylenecyclopropanes proceeded smoothly in the presence of catalytic amounts of Pd(PPh 3) 4, affording hydrocarbonation products in good to high yields. The ring opening of methylenecyclopropanes mainly occurred at the distal position to the exomethylene. In some cases, proximal bond cleavage also took place. The mode of ring opening depended upon both the structure of the pronucleophile and the substituent at the exomethylene carbon.

Reactions of co-ordinated ligands. Part 30. The transformation of methylenecyclopropanes into cationic η4-trimethylenemethanemolybdenum complexes, reactions with nucleophilic reagents, and the molecular structure of [Mo{η4-C(CH2)3}(CO)2(η-C5Me5)][BF4

Reaction of [Mo2(CO)6(η-C5Me5)2] with methylenecyclopropane and AgBF4 in CH2Cl2 affords the cationic trimethylenemethane complex [Mo{η4-C(CH2)3}(CO)2(η-C5Me5)][BF4]. Methylenecyclopropane and 2,2-dimethylmethylenecyclopropane react with [Mo(NCMe)2(CO)2(η-C5H5)][BF4] to give [Mo{η4-C(CH2)3}(CO)2(η-C5H5)][BF4] and [Mo{η4-C(CH2)2CMe2}(CO)2(η-C5H5)][BF4] respectively. A single-crystal X-ray diffraction study of [Mo{η4-C(CH2)3}(CO)2(η-C5Me5)][BF4] confirmed that ring opening of methylenecyclopropane had occurred. The complex crystallises in the centrosymmetric orthorhombic space group Pbca with a= 12.822(2), b= 12.311 (3), c= 22.660(4)A, and Z= 8 ion pairs. The structure has been solved by conventional methods and refined by full-matrix least squares to R= 0.0674 for 2 747 observed reflections at 268 ± 1 K. In the cation the trimethylenemethane ligand adopts an orientation that is syn with respect to the OC–Mo–CO angle. It is pyramidal with the CH2 groups bent towards the molybdenum atom by an average of 12.4°. There is intramolecular congestion involving the C5Me5 and C(CH2)3 ligands that may contribute towards the observed asymmetric bonding of the former to the metal atom. Extended Huckel molecular-orbital calculations suggest, that the observed syn stereochemistry is electronically preferred, and that the barrier to rotation of the η4-C(CH2)3 ligand relative to a Mo(CO)2(η-C5H5)+ fragment is high. The stereochemistry of the ring-opening reaction is disrotatory-out as exemplified by the conversion of cis-and trans-2,3-dimethylmethylenecyclopropane into syn,syn-dimethyl and syn,anti-dimethyl-trimethylene-methane complexes. The reaction of these cationic η4-trimethylenemethane complexes with the nucleophiles BH4–, OH–, CuMe2–, and SPh– affords η3-allylic complexes derived from attack on the peripheral carbons.

Reactions of co-ordinated ligands. Part XI. The ring opening of methylenecyclopropanes by palladium(II)–nucleophile systems: formation of substituted η3-but-3-enyl complexes of palladium(II)

trans- and cis-2,3-Dimethoxycarbonylmethylenecyclopropanes react with [Pd(MeCN)2Cl2] in dichloromethane to yield isomeric, ring-opened η3-[3-chloro-1,2-bis(methoxycarbonyl)but-3-enyl]palladium(II) complexes, via[Pd(η2-methylenecyclopropane)Cl2] intermediates. Analogous reactions in methanol, ethanol, isopropyl alcohol, and t-butyl alcohol solvents yield isomeric η3-[4-alkoxy-l,2-bis(methoxycarbonyl)but-3-enyl]palladium(II) complexes. 1H and 13C N.m.r. data for these, and derived, complexes are reported and discussed in terms of conformational isomerism within the chelating but-3-enyl ring. The mechanisms of these ring-opening reactions are discussed in terms of substituted cyclopropylmethyl-palladium intermediates, and the implications with respect to the mechanisms of chloropalladation and alkoxypalladation reactions of olefins are also reviewed.