- Sulphanilic acid as a recyclable bifunctional organocatalyst in the selective conversion of lignocellulosic biomass to 5-HMF
-
We herein report an unprecedented integrated process using organic salts as bifunctional organocatalysts under absolutely metal-free conditions for the conversion of a wide range of biomass-derived carbohydrates, cellulose, and even untreated lignocellulose (e.g. straw and barley husk) into 5-hydroxymethylfurfural (5-HMF) in a well-known water/MIBK biphasic solvent system.
- Mirzaei, Hamid M.,Karimi, Babak
-
-
Read Online
- Croos-Interaction Constants as a Measure of the Transition-State Structure. 14. Nucleophilic Substitution Reactions of 1-Phenyl-2-propyl Benzenesulfonates with Anilines in Methanol
-
The kinetics of the reactions between 1-phenyl-2-propyl benzenesulfonates (PPB) and anilines in methanol at 65.0 deg C are investigated, and the mechanism is discussed on the basis of various selectivity parameters, especially on the cross-interaction constants, ρij.The aryl participation is significant only with the p-CH3O-substituted substrate. ρXZ is positive, and accordingly the transition state (TS) variations with subbstituents are consistent with those predicted by the potential energy surface diagram.The TS is of an intermediate type between that for an associated (tight) and a dissociated (loose) SN2 process; it is rather tight, but bond breaking is ahead of bond making with positive charge development at the reaction center in the TS.The possibility of front-side attack witha four-center TS is precluded because of strong steric hinderance in a close approach of the two bulky groups, the nucleophile and leaving group, on the same side in the front-side attack.
- Lee, Ikchoon,Lee, Won Heui,Lee, Hai Whang
-
-
Read Online
- Rhodium(I)-catalyzed synthesis of aryltriethoxysilanes from arenediazonium tosylate salts with triethoxysilane
-
An efficient method for the preparation of aryltriethoxy-silanes from arenediazonium tosylate salts has been developed, which expands the substrates of rhodium-catalyzed silylation from iodides, bromides, and triflates to diazonium salts. A new method for hydrodediazoniation has also been explored.
- Tang, Zhi Yong,Zhang, Yuan,Wang, Tao,Wang, Wei
-
supporting information; experimental part
p. 804 - 808
(2010/06/14)
-
- Kinetics and mechanism of the aminolysis of cycloalkylmethyl arenesulfonates
-
Nucleophilic substitution reactions of cycloalkylmethyl arenesulfonates (CmH2n-1 CH2OSO2C6H4Z) with anilines (XC6H4NH2) in methanol at 65.0 °C were studied. The reactivity order (n=4>6>7>5) reflects largely the order of steric effect of the ring size (SEs term) except for n=5, which exhibits the least reactivity. This reversal of the order for n=5 is considered to result from large rate retardation due to polar effect of the ρ*σ* term. Application of the Taft equation to the rate data for n=5 and 6 gives ρ=17·4 and 5=2·3 with correlation coefficient of 0·90. The σ* values for n=4 and 7 are estimated to be - 0·23 and - 0·11, respectively. The positive ρxz values of ca 0·3 are consistent with previous results for the reactions at primary reaction centers.
- Oh, Hyuck Keun,Song, Se Jeong,Jo, Dong-Soo,Lee, Ikchoon
-
-
- KINETICS AND MECHANISM OF AMINOLYSIS OF PROPARGYL AND 1-METHYL-PROPARGYL ARENESULPHONATES
-
Kinetic studies were carried out on the aminolysis of propargyl and 1-methylpropargyl arenesulphonates in acetonitrile at 45.0 deg C.The cross-interaction constants, ρxz and βxz, are similar to, but smaller than, those for the SN2 processes at other primary and secondary carbon centers.Compared with the allyl series, the smaller magnitude of ρxz and βxz reflects a looser transition state, which in turn leads to a lower rate despite the greater Taft's ?* value and the lower intrinsic (ΔE0) and thermodynamic barriers (ΔE0).
- Oh, Hyuck Keun,Cho, In Ho,Jin, Min Jeong,Lee, Ikchoon
-
p. 629 - 633
(2007/10/02)
-
- Nucleophilic Substitution Reaction of Cumyl Arenesulfonates with Anilines
-
The nucleophilic substitution reaction of cumyl arenesulfonate with aniline has been investigated.The reaction in acetonitrile proceeds by the SN2 mechanism with probable frontside nucleophilic attack.The large magnitude of ρXZ (=-0.75) obtained results in an observable sign reversal of ρZ at ?'X = 0.83, with a negative ρZ value for ?X > ?'X.This rather unusual phenomenon can be rationalized by a strong interaction between the nucleophile and leaving group due to their close proximity in the transition state, which in turn is a result of the frontside nucleophilic attack.The reactions in methanol indicate that the SN1 channel competes with the SN2 pathway and ion-pair return is observed when the aniline nucleophhile concentration is low.
- Koh, Han Joong,Lee, Hai Whang,Lee, Ikchoon
-
p. 125 - 130
(2007/10/02)
-
- Bimolecular Nucleophilic Substitution (SN2) Reactions of Neopentyl Arenesulfonates with Anilines and Benzylamines in Methanol
-
Bimolecular nucleophilic substitution (SN2) reactions of neopentyl arenesulfonates with anilines and benzylamines in methanol at 55.0 deg C are reported.The tightness of the transition state (TS) is similar to that for other typical SN2 processes at a primary alkyl carbon centre based on the magnitude of the cross-interaction constant ρxz (0.30) between the substituents in the nucleophile (X) and leaving group (Z).The TS variation is in accord with that predicted by the potential energy surface diagram, which in turn is consistent with the positive sign of ρxz; a later TS is obtained with a weaker nucleophile and nucleofuge.Taft's polar substituent constant, ?*, for the trimethylsilyl group is estimated to be -0.48 by using a factor of 1.875 for the fall-off of ?* from the tert-butyl to the neopentyl group and extrapolating from the experimental Taft plot.
- Koh, Han Joong,Lee, Hai Whang,Lee, Ikchoon
-
p. 253 - 258
(2007/10/02)
-
- Nucleophilic Substitution Reactions of Indan-2-yl Arenesulfonates with Anilines in Methanol
-
The nucleophilic substitution reactions of (Y)-indan-2-yl (Z)-arenesulfonates with (X)-anilines in methanol at 55.0 deg C are reported.Sign reversals in all three second-order cross-interaction constants, ρXY, ρYZ and ρXZ, are observed at non-interaction points Z = -0.11 (ρXY = 0), X = -0.02 (ρYZ = 0) and Y = 0.43 (ρXZ = 0) respectively, which have been ascribed to an unusually large third-order cross-interaction constant, ρXYZ = -0.53, for the reaction series.An SN2 transition state with a tilted, parallel stacked and displaced structure of the three benzene rings in the nucleophile (X), substrate (Y) and leaving group (Z) is proposed to rationalize the strong three-body coupling manifested by the large ρXYZ value.
- Lee, Ikchoon,Lee, Young Sook,Huh, Chul,Lee, Hai Whang,Lee, Byung Choon
-
p. 2415 - 2418
(2007/10/02)
-
- Cross Interaction Constants As a Measure of Transition State structure. Part 7. Aminolysis of Alkyl Benzenesulphonates
-
Kinetic studies of the reactions of methyl and ethyl benzenesulphonates with anilines and benzylamines in methanol and acetonitrile at 65.0 deg C have been reported.The magnitudes of cross-interaction constants between substituents in the nucleophile (X) and the leaving group (Z),ρxz and βxz, were found to be greater for the ethyl series which indicates a tighter transition state for ethyl rather than methyl derivatives.This unexpected trend has been rationalized by making the assumption that the small electron-donating polar effect, of the α-methyl substituent in the ethyl compounds, requires a tighter transition-state structure in addition to the major effect of steric repulsion on the activation barrier which is present in all SN2 reactions taking place at a carbon centre.
- Lee, Ikchoon,Choi, Young Hoon,Rhyu, Keun Woo,Shim, Chang Sub
-
p. 1881 - 1886
(2007/10/02)
-
- Imides: Part IV - Synthesis and Reactions of N-(Arylsulphonyloxy)cyclohex-4-ene-1,2-dicarboximides
-
N-(Arylsulphonyloxy)cyclohex-4-ene-1,2-dicarboximides (IIa and IIb) undergo base-catalysed Lossen rearrangement with aromatic amines in refluxing ethanol to give mixtures of N-(2-arylcarbamoyl)cyclohex-4-enyl-N'-arylureas (IIIa-d) and the amine salts of arylsulphonic acids (IVa-h).Fusion of II with aromatic amines for 15 min gives mixtures of 3-arylquinazoline-2,4-diones (VIa-c) and IV; however fusion for 1 hr affords mixtures of sym-N,N'-diarylureas (VIIa-d) and IV.Compounds IIa and IIb also react with phenylhydrazine to give mixtures of VIII and phenylhydrazine saltof arylsulphonic acids (IXa and IXb).The mass spectra of IIb and IIIa are presented, and discussed.
- Aly, N. F.,El-Komy, M.,Aly, N. Y.,Orabi, M. O. A.
-
p. 471 - 476
(2007/10/02)
-
- Synthesis of Benzoquinazoline-2,4-diones via Lossen Rearrangement of N-(Arylsulphonyloxy)naphthalene-2,3-dicarboximide Derivatives
-
Treatment of N-(arylsulphonyloxy)-1-phenylnaphthalene-2,3-dicarboximides (IIa, b) with ammonia, aromatic amines, amino acids and hydrazine hydrate brings about the imide ring opening followed by Lossen rearrangement to give benzoquinazoline-2,4-diones (IIIa-h) and the salts of arylsulphonic acids (IVa-p).
- Hamed, A. A.,El-Bieh, A. A.,Baddawy, H. A.,Metwally, R. N.
-
p. 221 - 223
(2007/10/02)
-