7746-95-4Relevant academic research and scientific papers
1-[(E)-2-arylethenyl]-2,2-diphenylcyclopropanes: Kinetics and mechanism of rearrangement to cyclopentenes
Mulzer, Johann,Huisgen, Rolf,Arion, Vladimir,Sustmann, Reiner
experimental part, p. 1359 - 1388 (2011/10/09)
Kinetic measurements for the thermal rearrangement of 2,2-diphenyl-1-[(E)- styryl]cyclopropane (22a) to 3,4,4-triphenylcyclopent-1-ene (23a) in decalin furnished ΔHρm{{-{isom}^{ne }}}$=31.0±1.2kcal mol-1 and ΔSρm{{-{isom}^{ne }}}$=-6. 0±2.6e.u. The lowering of ΔHa‰ by 20kcal mol-1, compared with the rearrangement of the vinylcyclopropane parent, is ascribed to the stabilization of a transition structure (TS) with allylic diradical character. The racemization of (+)-(S)-22a proceeds with ΔHρm{{-{rac}^{ne }}}$=28.2±0.8kcal mol -1 and ΔSρm{{-{rac}^{ne }}}$=-5±2e.u., and is at 150° 106 times faster than the rearrangement. Seven further 1-(2-arylethenyl)-2,2-diphenylcyclopropanes 22, (E)- and (Z)-isomers, were synthesized and characterized. The (E)-compounds showed only modest substituent influence in their krac (at 119.4°) and kisom (at 159.3°) values. The lack of solvent dependence of rate opposes charge separation in the TS, but a linear relation of log krac with log p.r.f., i.e., partial rate factors of radical phenylations of ArH, agrees with a diradical TS. The ring-opening of the preponderant s-trans-conformation of 22 gives rise to the 1-exo-phenylallyl radical 26 that bears the diphenylethyl radical in 3-exo-position, and is responsible for racemization. The 1-exo-3-endo-substituted allylic diradical 27 arises from the minor s-gauche-conformation of 22 and is capable of closing the three- or the five-membered ring, 22 or 23, respectively. The discussion centers on the question whether the allylic diradical is an intermediate or merely a TS. Quantum-chemical calculations by Houk etal. (1997) for the parent vinylcyclopropane reveal the lack of an intermediate. Can the conjugation of the allylic diradical with three Ph groups carve the well of an intermediate? Copyright
Reaction of aromatic nitroso compounds with chemical models of 'thiamine active aldehyde'
Ferreira, Luísa M.,Marques, M. Manuel B.,Glória, Paulo M.C.,Chaves, Humberto T.,Franco, Jo?o-Pedro P.,Mourato, Isabel,Antunes, José-Rafael T.,Rzepa, Henry S.,Lobo, Ana M.,Prabhakar, Sundaresan
, p. 7759 - 7770 (2008/12/21)
Aromatic nitroso compounds in the presence of base and 2-(α-hydroxyalkyl)-3,4-dimethylthiazolium trifluoromethanesulfonate and related salts furnish in variable yields O- and N-acyl-aryl hydroxylamines and 3,4-dimethylthiazolium trifluoromethanesulfonate. A primary kinetic isotope effect of 4.9, obtained for the appropriate 2α-deuterated thiazolium salt, points to the C2α-H bond cleavage as the rate determining step. Radical species detected by ESR were unambiguously identified as phenylhydronitroxide, but attempted trapping of the corresponding C-heterocyclic radicals by TEMPO was not successful, and substrates incorporating a potential cyclopropyl radical clock gave products with the cyclopropyl ring intact. Theoretical calculations revealed a large activation energy for such reaction, which thus cannot per se exclude the intervention of such radical species. Evidence for the likely operation of two concurrent mechanisms, a radical and a preponderant ionic pathway, involving the conjugate base of the thiazolium salt, as the chemical model for 'active thiamine', and ArNO is presented for the formation of the products of the reaction.
Reactivity of cyclopropanic δ-oxo-α,β-unsaturated esters towards SmI2: 3-exo-trig cyclisation versus cyclopropane ring opening
Cammoun, Chama,Zriba, Riadh,Bezzenine-Lafollée, Sophie,Guibé, Fran?ois
, p. 3728 - 3736 (2007/10/03)
trans-(2′,2′-Diphenyl-bicyclopropyl-2-yl)-4,4-dimethyl-5-oxo-pent-2-enoic acid methyl ester 9, undergoes 3-exo-trig cyclisation in the presence of SmI2 without competitive ring opening of Newcomb's bicyclopropylic probe next to the carbonyl gro
Compatible injection and detection systems for studying the kinetics of excess electron transfer
Xu, Libin,Jin,Lal, Mukul,Daublain, Pierre,Newcomb, Martin
, p. 1837 - 1840 (2008/02/02)
A design for fast kinetic studies of electron transfer in radical anions is reported. α-Hydroxy radicals formed by 355 nm laser flash photolysis of α-phenacyl alcohols are deprotonated under basic conditions to give ketyl radical anions that serve as elec
Trans N-Methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] cycloprop-2-ene-1-carboxamides: Novel lipophilic kappa opioid agonists
Sabin,Horwell,McKnight,Broqua
, p. 291 - 296 (2007/10/03)
The synthesis and kappa opioid agonist activities of some lipophilic analogues of the kappa opioid agonist U-50488 incorporating motifs bearing two aromatic rings in place of the 3,4-dichlorophenyl group are described. Trans 2,3-diphenyl-N-methyl-N[2-(1-pyrrolidinyl)cyclohexyl]-2-cyclopropene-1 -carboxamide, 7, is a potent kappa opioid agonist. A diphenylcyclopropene analogue of CI-977, trans 2,3-diphenyl-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro[4.5]dec-8-yl]-2 -cyclopropene-1-carboxamide, 13, is a highly lipophilic chemically novel potent selective kappa opioid agonist.
X-ray Crystal Structure of the Dimeric tert-Butyl 2,2-Diphenylcyclopropanecarbothioate Lithium Enolate * TMEDA Complex: an "Ordinary" Ester Enolate Containing an "Ordinary" Methylenecyclopropane Moiety
Hahn, Ekkehardt,Maetzke, Thomas,Plattner, Dietmar A.,Seebach, Dieter
, p. 2059 - 2064 (2007/10/02)
After many unsuccessful attempts we now succeded in growing a suitable crystal of a cyclopropanecarbothioate lithium enolate (title compound 11c) for X-ray crystal structure analysis. 11c crystallizes as a tetramethylethylenediamine (TMEDA) complex in lar
