一种温和环醚开环成双酯的新方法

报道一种温和的环醚开环成双酯的新方法。以二氯甲烷为溶剂,五氧化二磷为氧化剂,异色满和醋酸铜于37℃开环反应10 h制得2-(2-乙酰氧基乙基)苄基乙酸酯,其结构经1H NMR,13C NMR和HR-ESI-MS确证。     

Exploiting Distal Reactivity of Coumarins: A Rhodium‐Catalyzed Vinylogous Asymmetric Ring‐Opening Reaction

While the utility of vinylogous enolates is well established in the setting of vinylogous aldol, Mannich, and Michael chemistries, literature reports concerning γ‐reactivity are scarce for other reaction classes. Presented herein is an unprecedented example of vinylogous reactivity exemplified by the rhodium‐catalyzed asymmetric ring‐opening reaction of oxabicycles. This strategy also provides a powerful route to incorporate the biologically useful coumarin motif into the hydronapthalene scaffold.     

Kinetics and Mechanism of the Reaction between an Arenediazonium Ion and Methyl Gallate (=Methyl 3,4,5‐Trihydroxybenzoate) in Aqueous Solution: Evidence for Diazo Ether Formation through an O‐Coupling Reaction

We have investigated the kinetics and mechanism of the reaction between 3‐methylbenzenediazonium ions (3MBD) and methyl gallate (=methyl 3,4,5‐trihydroxybenzoate; MG), in aqueous buffer solution by employing spectrophotometric (UV/VIS) and electrochemical (linear‐sweep voltammetry, LSV) techniques and computational methods. Because the absorption band of MG overlaps that of 3MBD, the reaction was monitored spectrophotometrically by measuring the changes in absorbance with time due to product formation, and biphasic kinetic profiles, indicative of accumulation of an intermediate in the course of the reaction, were obtained. The formation of an intermediate was confirmed by LSV. The observed rate constants k_obs for 3MBD disappearance were obtained by fitting the decrease in the peak current of the first reduction peak of 3MBD with time to the integrated first‐order equation. The variation of k_obs with [MG] was determined at different pH values and follows a saturation kinetic pattern. Alternatively, at a fixed [MG], k_obs values show an inverse dependence on [H⁺], suggesting that the reactive species is the anion and not the neutral form of MG. To discern which of the three OH groups of MG is the first one undergoing deprotonation, the geometries of the resulting anions were optimized by using B3LYP hybrid density functional theory (DFT) and a 6‐31G(++d,p) basis set. The deprotonation energies suggest that the OH group at the 4‐position is first deprotonated. The kinetic results can be accommodated, therefore, by assuming two competitive mechanisms, the spontaneous D_N+A_N decomposition involving 3MBD, and a mechanism involving an electrophilic attack at the O‐atom at C(4) in a pre‐equilibrium step, leading to the formation of a transient diazo ether of the type Ar? N?N? O? R which further decomposes. All attempts to isolate and characterize the diazo ether failed.     

合成硅氧醚的新方法：Silyltriflimides与醇或与醚反应

首次利用silyltriflimides［双－（三氟甲磺酰）－亚胺基硅烷］与醇或醚反应合成了一系列非环链状或环状的硅氧醚,反应产率较好。其中反应物silyl triflimides很容易由相应的苯基硅烷或丙烯基硅烷与HNTf2通过质子脱硅化反应得到。合成的新化合物的结构用1H NMR, 13C NMR, MS, IR 和HRMS等进行了表征.     

Ynamide Carbopalladation: A Flexible Route to Mono‐, Bi‐ and Tricyclic Azacycles

Bromoenynamides represent precursors to a diversity of azacycles by a cascade sequence of carbopalladation followed by cross‐coupling/electrocyclization, or reduction processes. Full details of our investigations into intramolecular ynamide carbopalladation are disclosed, which include the first examples of carbopalladation/cross‐coupling reactions using potassium organotrifluoroborate salts; and an understanding of factors influencing the success of these processes, including ring size, and the nature of the coupling partner. Additional mechanistic observations are reported, such as the isolation of triene intermediates for electrocyclization. A variety of hetero‐Diels–Alder reactions using the product heterocycles are also described, which provide insight into Diels–Alder regioselectivity.