2,3-二芳基马来酸酐环合反应机理的计算研究

在B₃LYP/6-311+G(d,p)//HF/3-21G水平上研究了2,3-二芳基马来酸酐环合反应机理.2,3-二芳基马来酸酐环合反应有两条反应途径:(1)反应过程中涉及的各种构型始终保持反式,即中心成环碳原子上的取代基团甲基或氢原子位于分子平面的异侧,这些构型具有C₂对称性;(2)反应过程中涉及的各种构型始终保持顺式,即中心成环碳原子上的取代基团甲基或氢原子位于分子平面的同一侧面,这些构型可具有Cs对称性.二芳基乙烯类化合物环合反应的位垒计算结果与Woodward-Hoffman原理一致,计算结果支持在环合碳原子上引入甲基能改善反应的热不可逆反应性能的实验结果.电荷分析表明,在环合碳原子上引入甲基,能增加二芳基乙烯类化合物体系对氧的稳定性,与实验结果一致.2,3-二芳基马来酸酐化合物的闭环结构的LUMO和HOMO能隙小于开环结构的能隙,说明闭环结构的最大吸收波长大于开环结构的最大吸收波长,与实验结果一致.     

Synthesis of Diaryl Ethers: A Long-Standing Problem Has Been Solved

A breakthrough in the synthesis of diaryl ethers has been achieved as shown in Equation (1). The coupling of phenols with aryl boronic acids in the presence of copper(II ) acetate and a base proceeds under very mild conditions (room temperature) as described simultaneously by Evans et al. and Chan et al. Examples: R¹=2-Cl, 2-I, 2-OMe, 4-tBu, 4-CH₂CH(NHCOOtBu)CO₂Me, 3,5-tBu₂; R²=2-Me, 3-OMe, 3-NO₂, 4-H, 4-F, 4-OMe.     

The unusual reaction of 2-isocyanatophenyl acetate with amines and water

The reaction of 2-isocyanatophenyl acetate with adamantyl and phenyl-containing amines gave the corresponding acetamides. Intermediate 2-isocyanatophenol formed in the course of the reaction undergoes intramolecular cyclization to 2-benzoxazolinone. These reactions proceed only with amines possessing basicity (pK_b > 3.80).     

Synthesis of diaryl sulfides through CH bond functionalization of arylamides with cobalt salt and elemental sulfur

A cobalt(II)-mediated, highly chemoselective thioarylation reaction of arylamides with elemental sulfur was reported. This reaction led to the formation of various symmetric diaryl sulfides in yields of up to 65% under mild reaction conditions. A cobalt-sulfur radical process was proposed based on preliminary results and mechanistic studies.     

Pd‐NHC catalysed Carbonylative Suzuki coupling reaction and its application towards the synthesis of biologically active 3‐aroylquinolin‐4 (1H)‐one and acridone scaffolds

We have unfolded a convenient and mild protocol for the synthesis of diaryl ketones via Pd‐ NHC catalysed carbonylative Suzuki coupling reaction. Notably, this method offers advantages like no use of toxic CO gas, shorter reaction time, high yield, and broad substrate scope. Several sensitive functional groups (like‐COMe, ‐COOMe, ‐F, ‐Cl, ‐Br, ‐NH₂, ‐CN) are well tolerated in this reaction. In addition, we have also demonstrated a new efficient route for the synthesis of biologically active and pharmaceutically important 2‐substituted 3‐Aroylquinolin‐4(1H)‐ones and acridone scaffolds.     

Pd-NHC-catalyzed synthesis of diaryl ketones

With N-hetereocyclic carbene and palladium catalysis, diaryl ketones with a variety of functional groups that span from electron withdrawing to electron donating substitutions can be conveniently synthesized using the corresponding aryl boronic acid and N-acyloxyphthalimide.     

Geminal systems. 50. Synthesis and alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas,carbamates, and benzamides

Procedures were developed for the synthesis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and benzamides by the reactions of the corresponding N-alkoxy-N-chloro derivatives with sodium carboxylates in MeCN. N-Chloro-N-ethoxy-p-toluenesulfonamide was inert in this reaction. Alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and tert-alkylamines afforded the corresponding N,N-dialkoxy derivatives, whereas alcoholysis of N-acetoxy-N-ethoxybenzamide gave rise to alkyl benzoates.     

Microwave‐Assisted Cross‐Coupling for the Construction of Diaryl Sulfides

The construction of diaryl sulfides through the cross‐coupling of aryl iodides and thiols in microwave heating is described. By using this method, a variety of diaryl sulfides can be prepared in a mild condition and in high yields. Deactivated 4‐nitrothiophenol was effective to afford the product in 94% yield. Sterically hindered ortho‐substituted aryl iodides or thiophenols provided diaryl sulfides effectively by this microwave‐assisted coupling reaction.     

Synthesis of substituted ureas possessing alkyl aromatic fragments via the reaction of 1-(3,3-diethoxypropyl)ureas with phenols

In this article, we report the approach to the substituted ureas based on the reaction of 1-(3,3-diethoxypropyl)ureas with phenols. Depending on the nature of the phenol and urea the reaction leads either to diarylpropane and dibenzoxanthene derivatives or calixarenes. The proposed method benefits from mild reaction conditions, high product yields and operational simplicity.