The rearrangement and solvolysis of furfuryl arenesulfinates

Furfuryl benzenesulfinate, furfuryl p-toluenesulfinate and 5-nitrofurfuryl benzenesulfinate were synthesized, and their behaviour under various conditions was investigated. The first two esters were found to undergo readily rearrangement to sulfone. In nonhydroxylic solvents, a mixture of furfuryl aryl sulfone and 2-methyl-3-furyl aryl sulfone is obtained. The ratio between the two sulfones changes with the polarity of the solvent. In hydroxylic solvents, only rearrangement to the furfuryl aryl sulfone takes place, and this is accompanied by solvolysis of the ester. A kinetic study of the reaction in ethanol and aqueous ethanol solvents indicated an ionization mechanism. It is suggested that under these conditions the sulfone is formed by recombination of ion pairs. A kinetic study of the rearrangement under nonsolvolytic conditions was also performed in order to obtain the effect of the solvent and the effect of added salts on the rate of rearrangement. This study has shown that the rate of rearrangement is sensitive to the ionizing power of the solvent. The addition of perchlorate was found to have a stronger effect on the formation of the furfuryl sulfone than on the 2-methyl-3-furyl sulfone. In this case an ionic mechanism is also suggested, and the two sulfones may arise by recombination from two different species of ion pairs.     

Base-catalysed solvolysis of acylsilanes

Kinetic studies have been made of the hydrolysis of XC₆H₄COSiR₃ compounds (R = Me, Et, Ph) in a mixture of THF (3 vol.) and aqueous sodium hydroxide (1 vol.). The rates of cleavage of p-NO₂C₆H₄CH₂SiMe₃, C₆H₅COSiMe₂C₆H₅ and C₆H₅COSiMe₂C₆H₄Cl-p compounds under the same conditions have also been measured. Electron-attracting substituents on either side of the bond being broken lead to an increase in the rate. For the XC₆H₄COSiR₃ compounds, the effects of the substituents X correlate excellently with their Hammett σ constants (? = 3.5 and 2.5 for R = Me and Ph, respectively). The data are consistent with a mechanism in which the attack of the hydroxide ion occurs at the carbonyl C atom.     

Copper induced solvolysis of sulfur compounds

The displacement of a phenylthio group by an acetate ion in some allylic or α-alcoxy sulfides and thioacetals was cleanly performed by treating them with a mixture of copper powder and cupric acetate in acetic acid.     

Mechanical properties of solvolysis lignin-derived polyurethanes

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG-MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.     

Thermal properties of solvolysis lignin-derived polyurethanes

Thermal properties of polyurethane (PU) films prepared from solvolysis lignin (SL), polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI) were examined by differential scanning calorimetry and thermogravimetry. In the SL—PEG—MDI system, the SL content, the molecular weight (M_n) of PEG and the NCO/OH ratio were changed in order to control the thermal properties. Glass transition temperatures (T_g's) of the prepared PU's were dependent on the SL content, the M_n of PEG and the NCO/OH ratio. However, the T_g of PU was significantly influenced by the SL content: the increment of T_g was ca. 150 K when the SL content in PEG increased from 0 to ca. 50%. The decomposition of the PU's was markedly dependent on the content of SL. Other factors, such as the NCO/OH ratio and the M_n of PEG, are less dominant compared with the SL content. This fact suggests that the dissociation between the isocyanate groups and the phenolic OH groups in SL may be the major factor in the whole process of the thermal decomposition of the PU containing SL     

Kinetics of solvolysis of 2-chloroquinoxaline

Pseudo-first-order rate constants and activation parameters have been measured for the solvolysis of 2-chloroquinoxaline in various aquo-organic mixtures using methanol, ethanol, and isopropanol as the organic solvent. Excellent linear correlations are found between lnk and the mol fraction of cosolvent and ln[H₂O]. The medium effect on the rates of solvolysis is assessed by Grunwald–Winstein's mY correlationship. The estimated values of m (0.55–0.72) and the entropy of activation (148–212 J deg^?1 mol^?1) for the reactions are well in the range for a bimolecular aromatic substitution reactions. © 1994 John Wiley & Sons, Inc.     

Synthesis of N-cyano-N-alkoxycarbonylalkylamino-symm-triazines and their solvolysis

The action of potassium salts of cyanoamino-symm-triazines on esters of chloroacetic and bromomalonic acids gave carbonylalkylamino-symm-triazines. The solvolysis of these esters proceeds with heterocyclilzation, leading to the formation of hydantoin derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1114–1116, August, 1993.     

Isomerization in ion pairs during solvolysis

Conclusions The isomerization of some bromoalkanol esters was studied, which is accompanied by the 1,2-migration of bromine. A mechanism was proposed for reactions of this type, which includes isomerization in the step of forming the ion pairs.The paper is published by order of the Editorial Board of this journal dated December 6, 1979.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2079–2085, September, 1980.     

Linear free energy relationships and solvolysis reactions

The validity of Grunwald-Winstein m values in relation to mechanistic designation of solvolysis reactions is examined. Stability-selectivity relationships in this area are shown to form examples of LFER's and not to emanate from correlations between selectivity and reactivity.     

Hammet correlations for the solvolysis of silylpyrroles

The siliconnitrogen bond in (XC₆H₄)Me₂SiNC₄H₄ (X = p-MeO, p-Me, m-Me, H, p-Cl) is cleaved in absolute ethanol containing sulphuric acid or amine buffers. The logarithms of the rate constants correlate with σ^o-constants, the p-values being -0.97 for the acid-catalysed reaction, and +1.8 and +2.6 for the reactions catalysed by amine and ethoxide anion, respectively. Mechanisms involving pentacoordinate silicon are suggested.     

Acetal formation by solvolysis of glucal-derived donor-acceptor cyclopropanes

The conversion of glucal derived donor-acceptor cyclopropanes to acetals by TiCl₄ mediated ring opening and alcohol trapping is described. Good selectivity for the alpha anomer and yields near 90% are consistently observed with aliphatic, benzylic and allylic alcohols, phenols and thiophenols. The utility of this method to prepare oligosaccharides through intermediate O,S-acetals is illustrated.     

Determination of benzoyl bisulphide by desulphurisation and solvolysis

Benzoyl disulphide is rapidly and quantitatively desulphurised to the monosulphide by reaction with triphenylphosphine in aqueous methanol at 25 degrees . The monosulphide reacts with methanol to form thiobenzoic acid and methyl benzoate. Benzoyl disulphide also reacts with methanol in solutions containing ammonium acetate or sodium acetate yielding thiobenzoic acid, methyl benzoate and elemental sulphur. Benzoyl disulphide and sulphur were detected by their polarographic reduction waves. Thiobenzoic acid was detected by its polarographic oxidation wave and yields were determined by amperometric silver nitrate titrations.     

A solvolysis route to a macrobicyclic allene

One of our objectives was to develop further access to large bicyclic tetrasubstituted olefins by cationic rearrangement. Among other things, such olefins can serve as valuable precursors to bicyclic tetrasubstituted allenese, and we report one such conversion by a new route that provided the first symmetrical member of this rare class of compounds. We synthesized the bicyclic trisubstituted olefins(Z)-bicyclo [10.5.0]heptadec-1(17)-ene (11) and (Z)-bicyclo[10.6.0]octadec-1(18)-ene (17) via an intramolecular Wittig reaction and a titanium mediated intramolecular reductive coupling, respectively. Olefins 11 and 17 were isomerized under acidic conditions to their tetrasubstituted counterparts (Z)-bicyclo[10.5.0]heptadec-1(12)-ene (12) and (Z)-bicyclo[10.6.0]octaladec-1(12)-ene (18). respectively. The previously reported tetrasubstituted olefin (Z)-bicyclo[11.11.0]tetracos-1(13)-ene (19) was further elaborated in a three step sequence to the allene bicyclo[11.11.0]pentacosa-1(25).13(25)-diene (22). Our approach involved dichlorocyclopiopanation of olefin 19 to cyclopropyl adduct 25,25-dichloro-tricyclo[11.11.1.0]pentacosane (20), silver assisted solvolysis of 20 to 25-chloro-1-methoxy-bicyclo[11.11.1]pentacos-13(25)-ene (21), and reductive elimination of 21 with zinc to allene 22.     

Cyclodextrin effect on solvolysis of substituted benzoyl chlorides

A kinetic study was carried out on the solvolysis of substituted benzoyl chlorides in the presence of alpha-, beta- and gamma-CD. Combination of the substituent dependent mechanism for solvolysis of benzoyl chlorides and the complexation ability of the cyclodextrin yields the following experimental behavior: (i) catalysis by beta- and gamma-CD for solvolysis of electron-attracting substituted benzoyl chlorides due to the reaction with its hydroxyl group C(6); (ii) absence of alpha-CD influence on solvolysis of benzoyl chlorides with electron withdrawing substituents; (iii) inhibition of solvolysis of benzoyl chlorides with electron-donating groups. This behavior is observed for solvolysis of meta/para substituted substrates in the presence of beta-CD, solvolysis of meta-substituted benzoyl chlorides in the presence of alpha-CD and solvolysis of para-substituted benzoyl chlorides in the presence of gamma-CD. This decrease in the rate constant is a consequence of the complexation of the substrate in the cyclodextrin cavity and its low solvation ability, causing the rate of solvolysis in its interior to be negligible. (iv) The solvolysis of meta-substituted benzoyl chlorides in the presence of gamma-CD yields a new behavior where the reaction of the complexed substrate is not negligible in the interior of the cyclodextrin cavity, which has been interpreted as a consequence of incomplete expulsion of hydration water from its cavity when the complexation takes place. (v) The experimental results obtained in the presence of alpha-CD show that meta-substituted benzoyl chlorides give rise to host : guest complexes with 1 : 1 stoichiometries, whereas those which are para-substituted cause a 2 : 1 stoichiometry to be formed. This difference in behavior has been interpreted taking into account the size of the different benzoyl chlorides and their accommodation in the alpha-CD cavity.