Home About us Contact
|
Home About us Contact | ||
|
|
||
Organoboronic Acids (organoboronic + acid)
Selected AbstractsRhodium-Catalyzed Asymmetric Conjugate Addition of Organoboronic Acids to Nitroalkenes Using Chiral Bicyclo[3.3.0] Diene Ligands,ANGEWANDTE CHEMIE, Issue 33 2010Zhi-Qian Wang Nichts geht über Diene: In der Titelreaktion mit anspruchsvollen Nitroalkenen ohne ,-Substituenten als Substraten und unter ArB(OH)2/KHF2 -Bedingungen waren chirale Bicyclo[3.3.0]-Diene die besten Liganden. Np = Naphthyl. [source] ChemInform Abstract: Rhodium-Catalyzed Chemo- and Stereoselective Arylative and Alkenylative Cyclization Reactions of Unsymmetric Diynes Containing a Terminal Alkyne Moiety with Organoboronic Acids.CHEMINFORM, Issue 38 2010Levent Artok Abstract A variety of 1,6-diynes containing a terminal alkyne, e.g. (I) or (IV), reacts with aryl- (II) or alkenylboronic acids (VI) with excellent chemo- and stereoselectivity in the presence of a Rh2(cod)2(O-Me)2 complex to give the 5-exo cyclization products, exclusively. [source] ChemInform Abstract: Efficient Synthesis of 3-Arylphthalides Using Palladium-Catalyzed Arylation of Aldehydes with Organoboronic Acids.CHEMINFORM, Issue 18 2010Masami Kuriyama Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Highly Regio- and Stereoselective Palladium(0)-Catalyzed Addition of Organoboronic Acids with 1,2-Allenic Sulfones, Sulfoxides, or Alkyl- or Aryl-Substituted Allenes in the Presence of Acetic Acid: An Efficient Synthesis of (E)-Alkenes.CHEMINFORM, Issue 52 2007Hao Guo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Palladium-Catalyzed Conjugate 1,4-Addition of Organoboronic Acids to ,,,-Unsaturated Ketones.CHEMINFORM, Issue 28 2006Tetsuya Yamamoto Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Palladium Pincer Complex Catalyzed Cross-Coupling of Vinyl Epoxides and Aziridines with Organoboronic Acids.CHEMINFORM, Issue 14 2006Johan Kjellgren Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A Highly Effective (Triphenyl phosphite)palladium Catalyst for a Cross,Coupling Reaction of Allylic Alcohols with Organoboronic Acids.CHEMINFORM, Issue 13 2005Yoshihito Kayaki Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Catalytic Cycle of Rhodium-Catalyzed Asymmetric 1,4-Addition of Organoboronic Acids.CHEMINFORM, Issue 37 2002-allylrhodium, Arylrhodium, Hydroxorhodium Intermediates. Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Cobalt(II)-Catalyzed Regio- and Stereoselective Hydroarylation of Alkynes with Organoboronic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2008Pao-Shun Lin Dr. Transmetallation: A series of cobalt-catalyzed highly regio- and stereoselective hydroarylations of alkynes with organoboronic acids, affording trisubstituted alkenes in high yield are described (see figure). [source] Palladium Pincer Complex Catalyzed Cross-Coupling of Vinyl Epoxides and Aziridines with Organoboronic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2005Johan Kjellgren Abstract Palladium-catalyzed cross-coupling of vinyl epoxides and aziridines with organoboronic acids was performed by using 0.5,2.5 mol,% pincer-complex catalyst. The reactions proceed under mild conditions affording allyl alcohols and amines with high regioselectivity and in good to excellent yields. Under the applied reaction conditions aromatic chloro-, bromo- and iodo substituents are tolerated. Our results indicate that the mechanism of the pincer complex catalyzed and the corresponding palladium(0) catalyzed process is substantially different. It was concluded that the transformations proceed via transmetalation of the organoboronic acids to the pincer-complex catalyst followed by an SN2,-type opening of the vinyl epoxide or aziridine substrate. In this process the palladium atom is kept in oxidation state +2 under the entire catalytic process, and therefore oxidative side reactions can be avoided. [source] Nickel-Catalyzed Mizoroki,Heck- versus Michael-Type Addition of Organoboronic Acids to ,,,-Unsaturated Alkenes through Fine-Tuning of LigandsCHEMISTRY - AN ASIAN JOURNAL, Issue 11 2007Pao-Shun Lin Abstract Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br2], ZnCl2, and H2O in CH3CN at 80,°C to give the corresponding Mizoroki,Heck-type addition products in good to excellent yields. Furthermore, 1,equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael-type addition was achieved in a very selective manner. Thus, various p- and o- substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH3CN at 80,°C for 12,h catalyzed by Ni(acac)2, P(o -anisyl)3, and K2CO3 to give the corresponding Michael-type addition products in excellent yields. However, for m- substituted arylboronic acids, the yields of Michael-type addition products are very low. The cause of this unusual meta -substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m- substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki,Heck-type products and dry reaction conditions for Michael-type addition products. Possible mechanistic pathways for both addition reactions are proposed. [source] Theoretical Study on the Mechanism of the Petasis-type Boronic Mannich Reaction of Organoboronic Acids, Amines, and , -Hydroxy AldehydesCHINESE JOURNAL OF CHEMISTRY, Issue 1 2010Jingcong Tao Abstract The mechanism of a typical Petasis-type boronic mannich reaction (the styrylboronic acid, dibenzylamine, and , -hydroxylpropionaldehyde) has been investigated using density functional theory calculations. According to our calculations, the reaction is most likely to proceed through the following steps: 1) the nucleophilic addition of the amine to the aldehyde to form the carbinolamine; 2) the dehydration of the carbinolamine; 3) the formation of the tetra-coordinated borate intermediate; 4) the CC bond formation by the intramolecular transfer of the styryl group; 5) the hydrolysis of the resulting intermediate to give the final products. The highest point on the energy profile is the transition state for the CC bond formation (118.8 kJ·mol,1 above the reactants in ethanol). Our results can give reasonable explanations on some experimental facts observed for many Petasis-type boronic Mannich reactions. [source] Rhodium-Catalyzed Formation of Stereocontrolled Trisubstituted Alkenes from Baylis,Hillman AdductsCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2009Thomas Gendrineau Abstract Efficient and general conditions for the formation of stereodefined trisubstituted alkenes by using the rhodium-catalyzed reaction of unactivated Baylis,Hillman adducts with either organoboronic acids or potassium trifluoro(organo)borates are reported (see scheme). We report here efficient and general conditions for the formation of stereodefined trisubstituted alkenes using the rhodium-catalyzed reaction of unactivated Baylis,Hillman adducts with either organoboronic acids and potassium trifluoro(organo)borates. The use of the [{Rh(cod)OH}2] precursor gave very fast coupling reactions under low catalyst loading, very mild reaction conditions (from room temperature up to 50,°C) and without the need of additional phosphane ligands. Based on the new reaction conditions, the reaction, originally limited to Baylis,Hillman adducts derived from esters, could be extended to a large variety of Baylis,Hillman adducts, bearing either keto, cyano or amido functionalities. Moreover, the reaction of Baylis,Hillman adducts bearing esters functionality was improved and could be conducted at lower temperature using lower catalyst loading. [source] Cobalt(II)-Catalyzed Regio- and Stereoselective Hydroarylation of Alkynes with Organoboronic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2008Pao-Shun Lin Dr. Transmetallation: A series of cobalt-catalyzed highly regio- and stereoselective hydroarylations of alkynes with organoboronic acids, affording trisubstituted alkenes in high yield are described (see figure). [source] Palladium Pincer Complex Catalyzed Cross-Coupling of Vinyl Epoxides and Aziridines with Organoboronic AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2005Johan Kjellgren Abstract Palladium-catalyzed cross-coupling of vinyl epoxides and aziridines with organoboronic acids was performed by using 0.5,2.5 mol,% pincer-complex catalyst. The reactions proceed under mild conditions affording allyl alcohols and amines with high regioselectivity and in good to excellent yields. Under the applied reaction conditions aromatic chloro-, bromo- and iodo substituents are tolerated. Our results indicate that the mechanism of the pincer complex catalyzed and the corresponding palladium(0) catalyzed process is substantially different. It was concluded that the transformations proceed via transmetalation of the organoboronic acids to the pincer-complex catalyst followed by an SN2,-type opening of the vinyl epoxide or aziridine substrate. In this process the palladium atom is kept in oxidation state +2 under the entire catalytic process, and therefore oxidative side reactions can be avoided. [source] Coupling reaction of organoboronic acids with chloropyrimidines and trichlorotriazine,CHINESE JOURNAL OF CHEMISTRY, Issue 9 2004Jiu-Qing Tan Abstract Pd-catalyzed cross-coupling reactions of chloropyrimidines with alkenylboronic acids readily proceed to give the corresponding alkenylpyrimidines in high to excellent yields. The coupling reaction of 2,4-dichloropyrimidine or 2,4,6-trichloropyrimidine with one equivalent of alkenylboronic acid occurred more easily on 4-position than on 2-position, which implied that the reaction is highly regioselective. The reaction is stereospecific since the configuration of C=C remained intact. The preliminary study on the cross-coupling reactions of 2,4,6-trichlorotriazine with one equivalent of arylboronic acids showed that the reactions afforded the monosubstituted triazines in moderate yields. The effect of steric hindrance of the substitutents on the reactions was found. [source] | ||||||||||