947-40-0Relevant articles and documents
A new and more efficient synthesis of methylene acetals
Chu, Guobiao,Zhang, Yanqiao,Li, Chunbao,Zhang, Yuqing
experimental part, p. 3828 - 3832 (2010/03/03)
A new and efficient synthesis of benzyl chlorides and methylene acetals by use of 2,4-dichloro-6-methoxy[l,3,5]triazine (MeOTCT) and dimethyl sulfoxide has been developed. Chlorides are the major products for benzyl alcohols, while methylene acetals are the major products for secondary alcohols. This procedure provides the highest yields so far for methylene acetals of steroids. A plausible mechanism is proposed on the basis of the experiments. Georg Thieme Verlag Stuttgart.
Non-linearity and non-additivity of substituent effects in solvolysis of 1,1-diphenylethyl p-nitrobenzoates
Uddin, Md. Khabir,Fujio, Mizue,Kim, Hyun-Joong,Rappoport, Zvi,Tsuno, Yuho
, p. 1371 - 1379 (2007/10/03)
The solvolysis rates of 1,1-diarylethyl p-nitrobenzoates and chlorides Y-Ar(X-Ar)CMe-LG (LG = OPNB, Cl) have been determined conductimetrically at 25°C in 80% (v/v) aqueous acetone. A linear Yukawa-Tsuno (Y-T) correlation was found for the symmetrical subseries (X = Y), showing a precise additivity relationship for the whole substituent range with ρsym = -3.78 and rsym = 0.77. The unsymmetrical subsets (X ≠ Y) gave statistically less reliable Y-T correlations, the apparent p value decreasing significantly when the fixed substituent Y becomes more electron-donating, which is in line with expectations from the Reactivity-Selectivity Relationship. In the whole dispersion pattern, both strong p-π-donor and electron-withdrawing substituents in any fixed-Y subsets exhibit significant rate-enhancement deviations from the points of X = Y on the reference ρsym line, which suggests an anti-Hammond shift of the transition state. However, there was a precise Extended Bronsted Linear Relationship between the pKR+ values for the hydration of 1,1-diarylethylenes and the rates of solvolysis of the p-nitrobenzoates with a slope of unity (α = 1.03). This is direct, convincing evidence that there is no significant shift of the transition-state coordinate over the whole range of substituent change.
Kinetic deuterium isotope effects as evidence for a common ion-pair intermediate in solvolytic elimination and substitution reactions of 1,1-diphenylethyl chloride
Thibblin, Alf,Sidhu, Harvinder
, p. 7403 - 7407 (2007/10/02)
Solvolysis of 1,1-diphenyl-1-chloroethane (1-Cl) in acetonitrile at 25°C provides the elimination product 1,1-diphenylethene (3). Addition of water or methanol to the acetonitrile increases the rate of elimination and gives rise to a second product, 1,1-diphenyl-l-hydroxyethane (1-OH) or 1,1-diphenyl-l-methoxyethane (1-OMe). The deuteriated analogue, 1,1- diphenyl-l-chloro[2,2,2-2H3]ethane (d-1-Cl), reacts slower. The overall kinetic deuterium isotope effect was found to decrease from (k12H + k13H)/(k12D + k13D) = 1.73 in pure acetonitrile to 1.34 in 20 vol % methanol in acetonitrile. This isotope effect is composed of a substitution isotope effect k12H/k12D and an elimination isotope effect k13H/k13D, which simultaneously change from 0.84 to 0.96 and from 2.2 to 3.2, respectively, when the methanol concentration is increased from 1.96 to 9.09 vol %. These results indicate a branched mechanism involving an almost rate-limiting formation of a common carbocationic intermediate. The acid-catalyzed solvolysis of 1,1-diphenyl-l-phenoxyethane (1-OPh) in acetonitrile containing 0.4 vol % aqueous 2 M sulfuric acid quickly provides the alcohol 1-OH, k12/k13 ≈ 11, which in a subsequent fast reaction yields the olefin 3 as the final product. In contrast, the solvolysis of the chloride 1-Cl in 0.4 vol % water in acetonitrile yields almost exclusively olefin 3, k12/k12 = 0.003. The results strongly indicate that the leaving chloride anion is involved in the elimination process and that the common intermediate is the contact ion pair. The isotope effect of the acid-catalyzed elimination of the alcohol 1-OH in 0.4 vol % water in acetonitrile is k13H/k13D = 5.3, which increases to k13H/k13D = 6.5 in 25 vol % acetonitrile in water. The possibility of an ion-molecule pair intermediate in the acid-catalyzed solvolysis is discussed.
