Criegee intermediate is believed to play an important role in the atmospheric chemistry.Because of its short life and the difficulty in experimental study, we carried out ah initio calculations on the thermochemistry ...Criegee intermediate is believed to play an important role in the atmospheric chemistry.Because of its short life and the difficulty in experimental study, we carried out ah initio calculations on the thermochemistry of the Criegee involving reactions in this study. Thermochemistrydata of reaction enthalpies and Gibbs free energies for four different stable structures of the Criegeeintermediates (singlet CH2OO ①1 A1 in C2v, triplet CH2OO ②3B1 in C2v, singlet CH2OO ③1A’ in Cs and triplet CH2OO ④ in C1 symmetry) involved in some of the gas-phase reactions were calculated at the standard Gaussian-2 [G2(MP2) and G2] and a modified G2, G2(fu1)[10],levels of theory. Relative energies among those Criegees and formic acid were compared. Chemical reactions incltlde the formation of Criegees, re-arrangement from Criegee to formic acid, dissociations (producing CH2(3B1)+O2, CH2(1A1)+O2, CO2+H2, CO2+2H, CO+H2O, OH+HCO) andthe reactions between Criegee and NO/H2O. Standard equilibrium constants for some reactions were investigated and may be obtained for all of the rest reactions involved in this study by the standard Gibbs free energies. It is shown that the formation of Criegee①-④ by ethylene and ozone, the re-arrangement from any Criegee to formic acid, the dissociation in producing CO2+O2and CO+H2O and the reactions between any Criegee and NO/H2O are all favourable thermodynamicaly. The dissociation in forming CO2+2H and OH+HCO is less favourable. While the dissociation in forming carbene (either in 3B1 or 1A1 state) is not allowed by values. Standard enthalpies of formation at 298 K for the four Criegees were predicted at the G2(ful) level of theory. Each value is the average value from ten of the above reactions and they are -4.3, 74.8,98.9 and 244.6 kJ mol-1 at the G2(ful) level for Criegee ① to Criegee ④, respectively. In addition, tile standard enthalpy of formation at 298 K for HOCH2OOH is further predicted to be -315.6 kJ mol-1 at the G2(MP2) level.展开更多
采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了Criegee中间体CH_3CHOO与OH自由基反应的微观机理.结果表明,上述反应存在抽氢、加成-分解和氧化3类反应通道,其中,syn-CH3CHOO+OH以抽β-H为优势通道,表观活化能为-4.88 k J/mol;anti-CH_3CHO...采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了Criegee中间体CH_3CHOO与OH自由基反应的微观机理.结果表明,上述反应存在抽氢、加成-分解和氧化3类反应通道,其中,syn-CH3CHOO+OH以抽β-H为优势通道,表观活化能为-4.88 k J/mol;anti-CH_3CHOO+OH则以加成-分解反应为优势通道,表观活化能为-13.25 k J/mol.在加成-分解和氧化反应通道中,anti-构象的能垒均低于syn-构象,而抽氢反应则是syn-(β-H)的能垒低于anti-构象.速率常数计算表明,anti-构象的加成-分解反应通道具有显著的负温度效应;syn-和anti-构象的氧化通道具有显著的正温度效应.3类反应具有显著不同的温度效应,说明通过改变温度可显著调节3类反应的相对速率.展开更多
采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了H2O及甲酸等6种有机酸对CH3CHOO与H2O加成反应的催化作用。结果表明,非催化反应存在双质子迁移和加成反应2条通道,其中加成反应为优势通道。其加成机理为H2O中OH加到CH3CHOO的α-C上,同时H2O...采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了H2O及甲酸等6种有机酸对CH3CHOO与H2O加成反应的催化作用。结果表明,非催化反应存在双质子迁移和加成反应2条通道,其中加成反应为优势通道。其加成机理为H2O中OH加到CH3CHOO的α-C上,同时H2O中另一个H迁移到CH3CHOO的端O上。催化剂H2O及有机酸以氢键复合物的形式参与反应促进了H质子转移,可降低基元反应能垒和表观活化能,且催化效应与有机酸的强度成正比。例如,当分别用H2O(p Ka=15.7)、甲酸(p Ka=3.75)和草酸(p Ka=1.23)催化时,生成syn-HAHP的基元反应能垒由非催化的69.12 k J?mol-1分别降至40.78、18.88和10.61 k J?mol-1。非催化反应具有正的表观活化能,而所有催化反应则均具有负的表观活化能。展开更多
采用CCSD(T)/aug-cc-p VTZ//M06-2X/cc-p VDZ方法研究了RCHOO(R=H,CH_3)+NO_2反应的微观机理,并讨论了甲基取代对反应活性的影响.结果表明,该反应存在加成-分解、氧化-氢转移和直接抽氢3类反应机理,其中氧化-氢转移反应的主要产物为RCO+...采用CCSD(T)/aug-cc-p VTZ//M06-2X/cc-p VDZ方法研究了RCHOO(R=H,CH_3)+NO_2反应的微观机理,并讨论了甲基取代对反应活性的影响.结果表明,该反应存在加成-分解、氧化-氢转移和直接抽氢3类反应机理,其中氧化-氢转移反应的主要产物为RCO+HNO_3,表观活化能仅为40.51 k J/mol,且释放出235.04 k J/mol的能量,是反应的优势通道;而生成RCHO+NO_3自由基的加成-分解通道较难进行.甲基取代使α-C电正性增大,端氧负性增加,这有利于加成-分解和氧化-氢转移反应的进行,但syn-CH_3CHOO中显著的位阻因素反而使加成-分解反应活性有所降低.展开更多
SGLT-2抑制剂中芳基取代基是影响药物活性强弱的关键,本研究以恩格列净为先导化合物,对其芳基取代基进行修饰改造,设计合成4种新的SGLT-2抑制剂关键中间体,采用分子对接技术验证其设计合理性,经过酰氯化、亲电取代、亲核取代、还原四步...SGLT-2抑制剂中芳基取代基是影响药物活性强弱的关键,本研究以恩格列净为先导化合物,对其芳基取代基进行修饰改造,设计合成4种新的SGLT-2抑制剂关键中间体,采用分子对接技术验证其设计合理性,经过酰氯化、亲电取代、亲核取代、还原四步反应合成出产率最高可达90.2%的SGLT-2抑制剂关键中间体。最终结构均经1H-NMR、13C-NMR、HRMS联合验证。该路线具有操作简便、绿色高效、产率高的特点。为筛选出高活性SGLT-2抑制剂提供新思路。The aryl substituents in SGLT-2 inhibitors are the key factors affecting the strength of drug activity. In this study, empagliflozin was taken as the lead compound, and its aryl substituents were modified and transformed to design and synthesize four new key intermediates of SGLT-2 inhibitors. The rationality of the design was verified by molecular docking technology. The key intermediates of SGLT-2 inhibitors with a maximum yield of 90.2% were synthesized through four-step reactions including acyl chlorination, electrophilic substitution, nucleophilic substitution and reduction. The final structures were all jointly verified by 1H-NMR, 13C-NMR and HRMS. This synthetic route has the characteristics of simple operation, being environmentally friendly, highly efficient and having a high yield. It provides new ideas for screening out highly active SGLT-2 inhibitors.展开更多
文摘Criegee intermediate is believed to play an important role in the atmospheric chemistry.Because of its short life and the difficulty in experimental study, we carried out ah initio calculations on the thermochemistry of the Criegee involving reactions in this study. Thermochemistrydata of reaction enthalpies and Gibbs free energies for four different stable structures of the Criegeeintermediates (singlet CH2OO ①1 A1 in C2v, triplet CH2OO ②3B1 in C2v, singlet CH2OO ③1A’ in Cs and triplet CH2OO ④ in C1 symmetry) involved in some of the gas-phase reactions were calculated at the standard Gaussian-2 [G2(MP2) and G2] and a modified G2, G2(fu1)[10],levels of theory. Relative energies among those Criegees and formic acid were compared. Chemical reactions incltlde the formation of Criegees, re-arrangement from Criegee to formic acid, dissociations (producing CH2(3B1)+O2, CH2(1A1)+O2, CO2+H2, CO2+2H, CO+H2O, OH+HCO) andthe reactions between Criegee and NO/H2O. Standard equilibrium constants for some reactions were investigated and may be obtained for all of the rest reactions involved in this study by the standard Gibbs free energies. It is shown that the formation of Criegee①-④ by ethylene and ozone, the re-arrangement from any Criegee to formic acid, the dissociation in producing CO2+O2and CO+H2O and the reactions between any Criegee and NO/H2O are all favourable thermodynamicaly. The dissociation in forming CO2+2H and OH+HCO is less favourable. While the dissociation in forming carbene (either in 3B1 or 1A1 state) is not allowed by values. Standard enthalpies of formation at 298 K for the four Criegees were predicted at the G2(ful) level of theory. Each value is the average value from ten of the above reactions and they are -4.3, 74.8,98.9 and 244.6 kJ mol-1 at the G2(ful) level for Criegee ① to Criegee ④, respectively. In addition, tile standard enthalpy of formation at 298 K for HOCH2OOH is further predicted to be -315.6 kJ mol-1 at the G2(MP2) level.
文摘采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了Criegee中间体CH_3CHOO与OH自由基反应的微观机理.结果表明,上述反应存在抽氢、加成-分解和氧化3类反应通道,其中,syn-CH3CHOO+OH以抽β-H为优势通道,表观活化能为-4.88 k J/mol;anti-CH_3CHOO+OH则以加成-分解反应为优势通道,表观活化能为-13.25 k J/mol.在加成-分解和氧化反应通道中,anti-构象的能垒均低于syn-构象,而抽氢反应则是syn-(β-H)的能垒低于anti-构象.速率常数计算表明,anti-构象的加成-分解反应通道具有显著的负温度效应;syn-和anti-构象的氧化通道具有显著的正温度效应.3类反应具有显著不同的温度效应,说明通过改变温度可显著调节3类反应的相对速率.
文摘采用CCSD(T)//B3LYP/6-311+G(d,p)方法研究了H2O及甲酸等6种有机酸对CH3CHOO与H2O加成反应的催化作用。结果表明,非催化反应存在双质子迁移和加成反应2条通道,其中加成反应为优势通道。其加成机理为H2O中OH加到CH3CHOO的α-C上,同时H2O中另一个H迁移到CH3CHOO的端O上。催化剂H2O及有机酸以氢键复合物的形式参与反应促进了H质子转移,可降低基元反应能垒和表观活化能,且催化效应与有机酸的强度成正比。例如,当分别用H2O(p Ka=15.7)、甲酸(p Ka=3.75)和草酸(p Ka=1.23)催化时,生成syn-HAHP的基元反应能垒由非催化的69.12 k J?mol-1分别降至40.78、18.88和10.61 k J?mol-1。非催化反应具有正的表观活化能,而所有催化反应则均具有负的表观活化能。
文摘采用CCSD(T)/aug-cc-p VTZ//M06-2X/cc-p VDZ方法研究了RCHOO(R=H,CH_3)+NO_2反应的微观机理,并讨论了甲基取代对反应活性的影响.结果表明,该反应存在加成-分解、氧化-氢转移和直接抽氢3类反应机理,其中氧化-氢转移反应的主要产物为RCO+HNO_3,表观活化能仅为40.51 k J/mol,且释放出235.04 k J/mol的能量,是反应的优势通道;而生成RCHO+NO_3自由基的加成-分解通道较难进行.甲基取代使α-C电正性增大,端氧负性增加,这有利于加成-分解和氧化-氢转移反应的进行,但syn-CH_3CHOO中显著的位阻因素反而使加成-分解反应活性有所降低.
文摘SGLT-2抑制剂中芳基取代基是影响药物活性强弱的关键,本研究以恩格列净为先导化合物,对其芳基取代基进行修饰改造,设计合成4种新的SGLT-2抑制剂关键中间体,采用分子对接技术验证其设计合理性,经过酰氯化、亲电取代、亲核取代、还原四步反应合成出产率最高可达90.2%的SGLT-2抑制剂关键中间体。最终结构均经1H-NMR、13C-NMR、HRMS联合验证。该路线具有操作简便、绿色高效、产率高的特点。为筛选出高活性SGLT-2抑制剂提供新思路。The aryl substituents in SGLT-2 inhibitors are the key factors affecting the strength of drug activity. In this study, empagliflozin was taken as the lead compound, and its aryl substituents were modified and transformed to design and synthesize four new key intermediates of SGLT-2 inhibitors. The rationality of the design was verified by molecular docking technology. The key intermediates of SGLT-2 inhibitors with a maximum yield of 90.2% were synthesized through four-step reactions including acyl chlorination, electrophilic substitution, nucleophilic substitution and reduction. The final structures were all jointly verified by 1H-NMR, 13C-NMR and HRMS. This synthetic route has the characteristics of simple operation, being environmentally friendly, highly efficient and having a high yield. It provides new ideas for screening out highly active SGLT-2 inhibitors.
