10066-31-6Relevant articles and documents
Wagner-Meerwein rearrangements in the gas phase: Anchimeric assistance to acid-induced dissociation of optically active phenylpropanols
Speranza, Maurizio,Filippi, Antonello
, p. 834 - 844 (1999)
The kinetics and the stereochemistry of Wagner-Meerwein rearrangements of O-protonated and O-methylated (S)-1-phenyl-2-propanol (1s(A)+; A=H or Me) and (S)-2-phenyl-1-propanol (2S(A)+; A=H or Me) have been investigated in the gas phase at 750 Torr and in the 25-140°C temperature range. The 1S(A) and 2S(A)+ intermediates were generated in the gas phase by reaction of the C(n)H5+(n=1, 2; A= H) and (CH3)2F+ ions (A - Me), formed by stationary γ radiolysis of bulk CH4 and CH3F, respectively, with the corresponding optically active alcohols. The results are consistent with unimolecular H2O loss from both 1s(H)+ and 2s(H); this is anchimerically assisted by all the groups adjacent to the leaving moiety. Anchimeric assistance appears much less efficient in both 1S(Me)+ and 2S(Me)+. Analysis of the activation parameters indicates that competing neighboring-group participation in C-O bond fission in 1s(H)+ and 2s(H) respond essentially to entropic rather than enthalpic factors. The stereochemical distribution of the reaction products allowed us to discern between backside and frontside phenyl-group participation in 1s(H+). The counterintuitive observation of a frontside Ph participation, with an activation energy 1.3±0.5 kcal mol-1 lower than that of the accompanying backside assistance, is attributed to conformational factors and to the stabilizing electrostatic interactions between the phenonium ion and the leaving H2O complex that is spatially allowed only in the frontside participation and forbidden in the backside one.
Highly efficient reduction of unactivated aryl and alkyl iodides by a ground-state neutral organic electron donor
Murphy, John A.,Khan, Tanweer A.,Zhou, Sheng-Ze,Thomson, Douglas W.,Mahesh, Mohan
, p. 1356 - 1360 (2007/10/03)
Electron-transfer reductions of unactivated aryl and alkyl iodides with a neutral ground-state organic molecule are reported. The reducing agent 1 is formed in two steps from N-methylbenzimidazole using very simple chemistry, and subsequent treatment of the iodoalkane or-arene with 1 affords cyclized products (see scheme).
Cross-interaction Constants as a Measure of the Transition State Structure. Part 11. Solvolyses of 1-Phenyl-2-propyl Benzenesulphonates
Lee, Ikchoon,Lee, Won Heui,Lee, Hai Whang,Lee, Byung Choon
, p. 785 - 791 (2007/10/02)
The solvolyses of 1-phenyl-2-propyl benzenesulphonates (PPBs) have been investigated in methanol-acetonitrile mixtures and in hexafluoropropan-2-ol (HFIP).The transition state structure has been discussed using various selectivity parameters, especially with the cross-interaction constants, ρYZ and λYZ, between substituents in the substrate (Y) and in the leaving group (Z).It has been found that the solvolysis proceeds by the solvent-assisted pathway, ks, in methanol, whereas in HFIP PPBs solvolyse via the aryl-assisted pathway, kΔ.The only exception was the p-MeO substituent, which deviates positively in methanol from the log ks vs. ? plot due to participation of the aryl-assisted path and negatively in HFIP from the log kΔ vs. ?(neophyl) plot due to deactivation by hydrogen bonding of the methoxy oxygen in the acidic solvent.The two distinctive high values of ρYZ provided evidence for the strongly bound transition states in the two processes, ks and kΔ, with a relatively low degree of bond breaking.
