- Single-pot access to bisorganoborinates: Applications in zweifel olefination
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Zweifel olefination is a catalyst-free reaction that serves alkene functionalization. While most methods employ commercially available boron pinacol esters, we have assembled a sequence in which the two partners of the formal coupling reaction are installed successively, starting from inexpensive boron alkoxides. The in situ formation of bisorganoborinates was accomplished by consecutive reaction of two different organometallic species. This single-pot procedure represents a great advancement in the generation of organoborinates and their involvement in C-C bond formation.
- Music, Arif,Baumann, Andreas N.,Spie?, Philipp,Hilgert, Nicolas,K?llen, Martin,Didier, Dorian
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supporting information
p. 2189 - 2193
(2019/04/10)
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- The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda-Grubbs Metathesis Catalysts
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Experimental studies of Hoveyda-Grubbs metathesis catalysts reveal important consequences of substitution at the 6-position of the chelating benzylidene ligand. The structural modification varies conformational preferences of the ligand that affects its exchange due to the interaction of the coordinating site with the ruthenium center. As a consequence, when typical S-chelated systems are formed as kinetic trans-Cl2 products, for 6-substituted benzylidenes the preference is altered toward direct formation of thermodynamic cis-Cl2 isomers. Activity data and reactions with tricyclohexylphosphine (PCy3) support also a similar scenario for O-chelated complexes, which display fast trans-Cl2?cis-Cl2 equilibrium observed by NMR EXSY studies. The presented conformational model reveals that catalysts, which cannot adopt the optimal nonchelating conformation of benzylidene ligand, initiate through a high-energy associative mechanism.
- Bieszczad, Bartosz,Barbasiewicz, Micha?
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supporting information
p. 10322 - 10325
(2015/07/07)
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- Simple and efficient synthesis of 4,7-dimethoxy-1(H)-indene
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Stirring 4,7-dimethoxy-1-indanol in chloroform at room temperature in the presence of a catalytic amount of p-toluenesulfonic acid gave 4,7-dimethoxy-1(H)-indene in quantitative yield. Other solvents, including benzene, which was the most frequently used one for this reaction, gave mostly polymeric materials. The new method was also effective for dehydration of other electron-rich benzylic alcohols. Copyright Taylor & Francis Group, LLC.
- Zhang, Xiang,Thimmaiah, Muralidhara,Fang, Shiyue
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p. 1873 - 1877
(2008/02/03)
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- Palladium-Catalyzed Cross-Coupling Reactions of Highly Hindered, Electron-Rich Phenol Triflates and Organostannanes
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The palladium-catalyzed cross-coupling reaction of highly hindered, electron-rich phenol triflates and organostannanes (Stille reaction) has been studied in a systematic manner.The following are its salient features: (1) electron-rich phenol triflates require triphenylphosphine to undergo palladium-catalyzed cross-couplings; (2) in general, efficient reactions take place only when larger-than-usual amounts (10-15percent) of palladium are employed.On the reagent side, alkyl- (methyl only), allyl-, vinyl- and alkinylstannanes undergo efficient cross-couplings with the titlesubstrates.However, some limitations to this novel entry to 2-substituted resorcinols exist in regard to both substrates and reagents.Thus, conformationally rigid (hexasubstituted) aryl triflates behave poorly, demethylation being an important side reaction.Moreover, alkyl groups other than methyl cannot be introduced because β elimination occurs more rapidly.The potentially powerful synthesis of hindered biaryls has also been studied briefly.In the present conditions, the reaction appears to be limited by the presence of ortho substituents on the arylstannane moiety.
- Saa, Jose M.,Martorell, Gabriel,Garcia-Raso, Angel
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p. 678 - 685
(2007/10/02)
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- Palladium catalyzed cross-coupling of phenol triflates with organostannanes. A versatile approach for the synthesis of substituted resorcinol dimethyl ethers.
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2,6-Dimethoxy-substituted phenol triflates undergo efficient Pd(0) catalyzed cross coupling with organostannanes, thus providing an easy access to substituted resorcinol dimethyl ethers, a common building block of many aromatic polyketides.
- Martorell, Gabriel,Garcia-Raso, Angel,Saa, Jose M.
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p. 2357 - 2360
(2007/10/02)
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