نتایج جستجو برای: phase transfer catalysis

تعداد نتایج: 893887  

2014
Dacheng Zhang Xiaoshuang Gao Tanyu Cheng Guohua Liu

The construction of chiral biaryl alcohols using enantio-relay catalysis is a particularly attractive synthetic method in organic synthesis. However, overcoming the intrinsic incompatibility of distinct organometallic complexes and the reaction conditions used are significant challenges in asymmetric catalysis. To overcome these barriers, we have taken advantage of an enantio-relay catalysis st...

2008
Takuya Hashimoto Keiji Maruoka

In 1971, Starks introduced the term “phase-transfer catalysis” to explain the critical role of tetraalkylammonium or phosphonium salts (QþX ) in the reactions between two substances located in different immiscible phases [1]. For instance, the displacement reaction of 1-chlorooctane with aqueous sodium cyanide is accelerated many thousand-fold by the addition of hexadecyltributylphosphonium bro...

2014
Xiaoyu Yang Robert J. Phipps F. Dean Toste

We report a study involving the successful merger of two separate chiral catalytic cycles: a chiral anion phase-transfer catalysis cycle to activate Selectfluor and an enamine activation cycle, using a protected amino acid as organocatalyst. We have demonstrated the viability of this approach with the direct asymmetric fluorination of α-substituted cyclohexanones to generate quaternary fluorine...

Journal: :Organic & biomolecular chemistry 2016
R N Prasad Tulichala K C Kumara Swamy

The divergent behaviour of 3-alkynylindole-2-carboxamides, under palladium catalysed conditions and phase-transfer catalytic conditions, is described. Thus, palladium catalysed intramolecular C-N and C-C bond formation in a single step by C-H activation involving 3-alkynylindole-2-carboxamides and leading to pyrrolodiindolones in high yields is developed. In contrast, using the same precursors,...

Journal: :Journal of the American Chemical Society 2015
Hosea M Nelson Brett D Williams Javier Miró F Dean Toste

A palladium-catalyzed three-component coupling of α-olefins, aryldiazonium salts, and bis(pinacolato)diboron affords direct access to chiral benzylic boronic esters. This process is rendered highly enantioselective using an unprecedented example of cooperative chiral anion phase transfer and transition-metal catalysis.

Journal: :Molecules 2012
Rosa M Suárez Maria Paz Matía José Luis Novella Andres Molina Antonio Cosme Juan José Vaquero Julio Alvarez-Builla

The synthesis of 9,9'-[1,2-ethanediylbis(oxymethylene)]bis-2-amino-1,9-dihydro-6H-purin-6-one, a minor impurity of acyclovir, is described. Starting with commercial N-(9-acetyl-6-oxo-1H-purin-2-yl)acetamide, the process uses an acid catalysed phase transfer catalysis (PTC) process to produce the selective alkylation at the 9 position of the guanine ring.

2009
Ling-hua Zhuang Guo-wei Wang

The title compound, C(12)H(14)O(6), was prepared by the Williamson reaction of 1,4-dihydroxy-benzene and methyl chloro-acetate with phase-transfer catalysis. The compound lies on an inversion center. The structure is stabilized by weak C-H⋯π inter-actions.

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