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131.
Anne-Marie Caminade Jean-Pierre Majoral Valérie Maraval Rosa-Maria Sebastián 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1493-1497
Several series of phosphorus-containing dendrimers have been designed to study the variation of their properties, depending on the type, the location (surface, branches, core, and cavities), and the number of functions implied. 相似文献
132.
133.
传统的傅-克酰基化反应以酰氯或酸酐作为酰化剂、路易斯酸作为催化剂。大量路易斯酸催化剂及反应产生的氯化氢都需要后处理,并且酰氯对湿度敏感,储存及使用过程中易发生危险。而以三氟乙酸酐作为活化剂、直接以羧酸作为酰化剂的酰化反应不需要事先将羧酸制成酰氯、酸酐或酰胺,且活化剂三氟乙酸酐及副产物三氟乙酸都能很容易地通过蒸馏回收,因此,这类酰化反应能有效解决传统的傅-克酰基化反应所存在的问题。本文综述了近20年来以三氟乙酸酐作为活化剂、直接以羧酸作为酰化剂的酰化反应方法的发展,以及其在功能有机分子、药物分子和天然产物合成中的应用。 相似文献
134.
Dr. Masaru Kondo Dr. Shinobu Takizawa Yuzhao Jiang Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9866-9869
The Mills reaction and cyclization of readily available 2-aminobenzyl alcohols and nitrosobenzenes using thionyl bromide provided 2H-indazoles in up to 88 % yields. In the metal-free process, acetic acid played a crucial role for the both Mills reaction and cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence. 相似文献
135.
Treatment of 2‐bromoaryl pyrrole/indol‐2‐yl ketones with cesium carbonate in DMF resulted in the formation of 9H‐pyrrolo[1,2‐a]indol‐9‐ones and 10H‐indolo[1,2‐a]indol‐10‐ones in moderate to excellent isolated yields. 相似文献
136.
An asymmetric anti-aldol addition process of ketone-derived donors that is not limited by the structure of the ketone is described. This is achieved by merging the enantioselective α,α-bisalkylation of N-amino cyclic carbamate (ACC) hydrazones with the asymmetric anti-aldol addition of ACC hydrazones. The products of this process are obtained with essentially perfect stereoselectivity. Using this procedure it is possible to gain access to ketone-based anti-aldol addition products that are inaccessible in a controlled sense via direct aldol methods. 相似文献
137.
Dipl.‐Chem. Sascha A. Erhardt Dr. Florian Hoffmann Dr. Jürgen O. Daiß Dr. Jürgen Stohrer Dr. Eberhardt Herdtweck Prof. Dr. Bernhard Rieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4818-4825
(Acetoxymethyl)silanes 2 , 7 a – c , and 10 a – c with at least one alkoxy group, of the general formula (AcOCH2)Si(OR)3?n(CH3)n (R: Me, Et, iPr; n=0, 1, 2), were synthesized from the corresponding (chloromethyl)silanes 1 , 6 a – c , and 9 a – c by treatment with potassium acetate under phase‐transfer‐catalysis conditions. These compounds were found to provide 2,2,5,5‐organo‐substituted 1,4‐dioxa‐2,5‐disilacyclohexanes 3 , 8 a – c , and 11 a – c if treated with organotin(IV) catalysts such as dioctyltin oxide. The reaction proceeds through transesterification of the acetoxy and alkoxy units followed by ring‐closure to form a dimeric six‐membered ring. The corresponding alkyl acetates are formed as the reaction by‐products. With these mild conditions, the method overcomes the drawbacks of previously reported synthetic routes to furnish 2,2,5,5‐tetramethyl‐1,4‐dioxa‐2,5‐disilacyclohexane ( 3 ) and even allows the synthesis of 1,4‐dioxa‐2,5‐disilacyclohexanes bearing hydrolytically labile alkoxy substituents at the silicon atom in good yields and high purity. These new materials were fully characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and X‐ray analysis (trans‐ 8 a ). 相似文献
138.
Dr. Randa K. Gabr Prof. Dr. Takuji Hatakeyama Prof. Dr. Kazuhiro Takenaka Prof. Dr. Shinobu Takizawa Yoshihiro Okada Prof. Dr. Masaharu Nakamura Prof. Dr. Hiroaki Sasai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(29):9518-9525
The reaction pathway of an enantioselective 5‐endo‐trig‐type cyclization of 3‐alkenoic acids catalyzed by a chiral palladium–spiro‐bis(isoxazoline) complex, Pd–SPRIX, has been studied by density functional theory calculations. The most plausible pathway involves intramolecular nucleophilic attack of the carboxylate moiety on the C?C double bond activated by Pd–SPRIX and β‐H elimination from the resulting organopalladium intermediate. The enantioselectivity was determined in the cyclization step through the formation of a π‐olefin complex, in which one of the two enantiofaces of the olefin moiety was selected. The β‐H elimination occurs via a seven‐membered cyclic structure in which the acetate ligand plays a key role in lowering the activation barrier of the transition state. In the elimination step, the SPRIX ligand was found to behave as a monodentate ligand due to the hemilability of one of the isoxazoline units thereby facilitating the elimination. Natural population analysis of this pathway showed that the more weakly electron‐donating SPRIX ligand, compared with the bis(oxazoline) ligand, BOX, facilitated the formation of the π‐olefin complex intermediate, leading to a smaller overall activation energy and a higher reactivity of the Pd–SPRIX catalyst. 相似文献
139.
3,4‐Diacetylhexane‐2,5‐dione (tetra‐acetylethane) undergoes a complex reaction with primary amines in boiling water to produce N‐alkyl‐3‐acetyl‐2,5‐dimethylpyrroles, together with small quantities of N‐alkyl‐3,4‐diacetyl‐2,5‐dimethylpyrroles and 2,5‐dimethyl‐1H‐pyrrol‐3‐yl‐vinyl‐acetamides. When the reaction was carried out in methanol at room temperature, the yields of the latter products increased. 相似文献
140.
The tin hydride–mediated cyclization of a number of sulfides and sulfones under mild and neutral conditions has been investigated. The sulfides were in turn derived from 3(2H) benzothiofuranone and 2‐bromobenzyl bromides by phase‐transfer‐catalyzed reaction, and the corresponding sulfones were prepared by treatment of the corresponding sulfides with m‐CPBA at room temperature. The sulfides and sulfones were then reacted with n Bu3SnH‐AIBN to afford regioselectively benzofuran‐annulated six‐membered sulfur heterocycles. 相似文献