33695-59-9Relevant articles and documents
Side-chain fragmentation of arylalkanol radical cations. Carbon-carbon and carbon-hydrogen bond cleavage and the role of α- and β-OH groups
Baciocchi, Enrico,Bietti, Massimo,Putignani, Lorenza,Steenken, Steen
, p. 5952 - 5960 (2007/10/03)
A product analysis and kinetic study of the one-electron oxidation of a number of 1-arylpropanols, 1,2-diarylethanols, and some of their methyl ethers by potassium 12-tungstocobaltate(III) (abbreviated as Co(III)W) in aqueous acetic acid was carried out and complemented by pulse radiolysis experiments. The oxidations occur via radical cations which undergo side-chain fragmentation involving the C(α)-H and/or C(α)-C(β) bond. With 1-(4-methoxyphenyl)-2-methoxypropane (1), only deprotonation of the radical cation is observed. In contrast, removing the ring methoxy group leads to exclusive C-C bond cleavage in the radical cation. Replacing the side-chain β-OMe by β-OH, the radical cation undergoes both C-C and C-H bond cleavage, with both pathways being base catalyzed. C-C bond breaking in the radical cation is also enhanced by an α-OH group, as shown by 1-(4-methoxyphenyl)-2,2-dimethyl-1-propanol (7), where this pathway, which is also base catalyzed, is the only one observed. Interestingly, α- and β-OH groups exhibit a very similar efficiency in assisting the C-C bond cleavage route in the radical cations, as is evident from the kinetic and products study of the oxidation of 1-phenyl-2-(4-methoxyphenyl)ethanol (5) and 1-(4-methoxyphenyl)-2-phenylethanol (6) by Co(III)W, and from pulse radiolysis experiments on 5 and 6. C-C bond cleavage is the main reaction for both radical cations which exhibit a very similar rate of fragmentation (k = 2.0 and 3.2 x 104 s-1, respectively). In both fragmentation reactions a small solvent isotope effect, k(H2O)/k(D2O) (1.4 for 5.+ and 1.2 for 6.+) and negative activation entropies are observed. These data suggest that a key role in the assistance by α- or β-OH groups to C-C bond cleavage is played by hydrogen bonding or specific solvation of these groups. The kinetic study of the oxidations promoted by Co(III)W has also shown that when only one group, OH or OMe, is present in the side chain (either on C(α) or C(β)), the fragmentation step or both the electron transfer and fragmentation steps contribute to the overall oxidation rate. However, with an OH group on both carbons of the scissile bond, as in 1-(4-methoxyphenyl)-1,2-propanediol (9), the rate of C-C bond cleavage is so fast that the electron transfer step becomes rate determining.
The Influence of Borate Buffers on the Hydration Rate of Cyanohydrins: Evidence for an Intramolecular Mechanism
Jammot, Jacqueline,Pascal, Robert,Commeyras, Auguste
, p. 157 - 162 (2007/10/02)
The effects of borate buffers on the pseudo first-order rate constants for the hydration of hydroxyacetonitrile (1) have been examined on the pH range 8.6-10.3 at 80 deg C.Kinetic results are compatible with a reaction of the neutral cyanohydrin with borate anion or any other kinetically equivalent mechanism.Cyanohydrin structural effects are consistent with a pathway involving the pre-equilibrium formation of a borate-substrate adduct, followed by a rate-determining intramolecular nucleophilic attack on the nitrile group.Phenylboronate ion has also been shown to act as an efficient catalyst, but it was not possible to detect any influence due to disubstituted borate ions.Thus, it is suggested that a trigonal borate anion actually acts as a nucleophile.
CYANOTRIMETHYLSILANE AS A VERSATILE REAGENT FOR INTRODUCING CYANIDE FUNCTIONALITY
Utimoto, Kiitiro,Wakabayashi, Yukio,Horiie,Takafumi,Inoue, Masaharu,Shishiyama, Yuho,et al.
, p. 967 - 974 (2007/10/02)
Cyanotrimethylsilane adds to some α,β-unsaturated ketones in conjugate manner under the catalytic action of Lewis acids such as triethylaluminium, aluminium chloride, and SnCl2.Hydrolysis of the products gives β-cyano ketones which are identical to the hydrocyanated products of the starting enones.The title silicon reagent reacts with acetals and orthoesters under the catalytic action of SnCl2 or BF3*OEt2 affording 2-alkoxy- and 2,2-dialkoxyalkanenitriles.Application of the reaction to O-protected β-D-ribofuranoses gives selectively β-D-ribofuranosyl cyanide in excellent yield.
2-ALKOXY AND 2,2-DIALKOXY NITRILES FROM ACETALS AND ORTHOESTERS --- EXCHANGE OF ALKOXY INTO CYANO GROUP BY MEANS OF CYANOTRIMETHYLSILANE
Utimoto, Kiitiro,Wakabayashi, Yukio,Shishiyama, Yuho,Inoue, Masaharu,Nozaki, Hitosi
, p. 4279 - 4280 (2007/10/02)
Title transformation is accomplished by the catalytic action of SnCl2 or BF3*OEt2.Lithio derivative of 2,2-dimethoxyacetonitrile is used as synthetic equivalent of methyl lithioformate.
