79644-39-6Relevant academic research and scientific papers
Solvolysis of substituted benzyl azoxyarenesulfonates: Characterisation of the transition state and the selectivity of benzylic intermediates in 50% aqueous 2,2,2-trifluoroethanol
Gordon,Maskill
, p. 2059 - 2062 (2007/10/03)
Thirteen substituted benzyl azoxyarenesulfonates have been prepared and rate constants for solvolysis of twelve have been measured in 50% (v/v) aqueous 2,2,2-trifluoroethanol over a range of temperatures from which activation parameters and rate constants at 25°C have been determined. A six-point Hammett correlation for substituents in the benzylic electrofuge, with azoxytoluene-p-sulfonate as the common nucleofuge, gives ρ(σ+) = -3.27. With 4-methylbenzyl as a common electrofuge, four substituents in the azoxybenzenesulfonate nucleofuge give ρ(σ) = 1.07. Comparison with model reactions indicates a synchronous concerted rate-limiting fragmentation for these substrates. With the less reactive 3-chlorobenzyl as electrofuge, ρ for substituents in the nucleofuge is only ca. 0.7 which indicates a lower degree of charge development in the arenesulfonate in the transition state for these reactions. Product analyses have been carried out for compounds of high, intermediate, and low reactivity. These indicate a reactivity-selectivity relationship for capture of the substituted benzylic electrophiles by water and 2,2,2-trifluoroethanol. Substituted benzaldehydes are formed from the less reactive substrates, indicating trapping of the first-formed benzylic carbenium ion by nitrous oxide and subsequent elimination of nitrogen and a proton; but yields are low and decrease as the substituted benzyl cation becomes increasingly stable.
Phenyl Cations as Reactive Intermediates in the Solvolysis of Dien-in-yl Triflates
Holweger, Walter,Hanack, Michael
, p. 3004 - 3020 (2007/10/02)
The synthesis, separation, and solvolysis of the stereoisomeric 1,4-dimethyl-1,3-hexadien-5-yn-1-yl triflates 15a - c in various solvents are described.In contrast to the (Z)-isomers 15a - c, the (E)-isomers 15a - c react preferably via an intermediate phenyl cation 16 to give the phenyl ethers 17.Further mechanistic investigations which support the formation of the intermediate phenyl cations 16 are described.The formation of the benzylic derivatives 18 is discussed.
Experimental Evidence for a Phenyl Cation Intermediate in the Solvolysis Reactions of Dienynyl Trifluoromethanesulphonates
Hanack, Michael,Holweger, Walter
, p. 713 - 714 (2007/10/02)
The synthesis, separation, and solvolysis of the stereoisomeric dienynyl trifluoromethanesulphonates (1) are described, whereby the E-isomers, in contrast with the Z-isomers, rearrange to a remarkable extent to form the phenyl ethers (5) via the phenyl cations (2).
