62153-61-1Relevant academic research and scientific papers
On the substituent effects of the thermal ethenylcyclopropane-to-cyclopentene rearrangement: Gas-phase kinetics of ethoxy-, methylthio-and trimethylsilyl-substituted ethenylcyclopropanes
McGaffin, Gregory,Grimm, Bernd,Heinecke, Ute,Michaelsen, Holger,De Meijere, Armin,Walsh, Robin
, p. 3559 - 3573 (2001)
A series of 1- and 2-substituted ethenylcyclopropanes were prepared in high yields and subjected to gas-phase pyrolytic kinetic investigations. All ethenylcyclopropanes rearranged cleanly to the correspondingly substituted cyclopentenes, although in the case of the 2-substituted compounds, cis/trans isomerization was additionally observed (both stereoisomers were investigated in these cases). All rearrangements obeyed first-order kinetics independent of pressure and surface-to-volume ratio. Reasonable Arrhenius parameters were obtained for these homogeneous, unimolecular reactions. 1-Trimethylsilyl and 1-methylthio substituents produced modest rate accelerations, consistent with biradical mechanisms. A previous finding of rate retardation by 1-trimethylsilyl substitution is attributed to steric hindrance. 2-Ethoxy and 2-methylthio substituents [in both (E)- and (Z)-configurations] produced greater rate accelerations, inconsistent with biradical mechanisms. The steric effects on the kinetics of the (Z)-isomer rearrangements appear relatively unimportant. The methylthio substituent effects are documented and analyzed for the first time. Wiley-VCH Verlag GmbH, 2001.
Dirhodium(II) tetraacetate catalyzed (chlorovinyl)cyclopropanation of enol ethers and dienol ethers - A route to donor-substituted vinylcyclopropanes, ethynylcyclopropanes and cycloheptadienes
De Meijere,Schulz,Kostikov,Graupner,Murr,Bielfeldt
, p. 547 - 560 (2007/10/02)
2-Chloro- (4-Cl), 3,3-dichloro- (4-Cl2), and 2,3,3-trichlorodiazo-propene (4-Cl3) can easily be prepared in up to 70% yield by thermal fragmentation (Bamford-Stevens reaction), at 60°C in tetrahydrofuran, of the corresponding chloroacrolein tosylhydrazone sodium salts 3-Cl(n). Tetrahydrofuran solutions of (chlorovinyl)diazomethanes 4-Cl(n) thus obtained are used for cyclopropanation reactions of a large variety of alkenes. Under dirhodium(II) tetraacetate catalysis, yields of (chlorovinyl)cyclopropanes 6-Cl(n) [and of vinylcyclopropanes 6-H3 with diazopropene (4-H3)] are quite good especially from enol ethers. Dienol silyl ethers, 2-trimethylsiloxy-1,3-butadiene (12) and 1-(1'-trimethyl-siloxyvinyl)cyclohexene (15), react exclusively at the donor-substituted double bond, the resulting 1-siloxy-1,2-divinylcyclopropanes 13-X(n), 16-X(n) readily rearrange to cycloheptadiene derivatives 14 and 17-20 respectively. 2-Alkoxy-1-(chlorovinyl)cyclopropanes such as 6 o-Cl2, 6 p-Cl2, 6 p-Cl3 can be transformed to synthetically valuable 2-alkoxy-1-ethynylcyclopropanes 27 o,p, which are also obtained by direct ethynylcyclopropanation of enol ethers with diazopropyne (28). This latter method provides the first known access to 2-siloxy-1-ethynylcyclopropane 25m.
