1338073-35-0Relevant academic research and scientific papers
Free Radical Pathway Cleavage of C—O Bonds for the Synthesis of Alkylboron Compounds
Lu, Xi,Zhang, Zhen-Qi,Yu, Lu,Zhang, Ben,Wang, Bing,Gong, Tian-Jun,Tian, Chang-Lin,Xiao, Bin,Fu, Yao
supporting information, p. 11 - 18 (2018/12/13)
We report a silver-catalyzed borylation of alkyl tosylates, which provides a new method for the synthesis of alkylboron compounds with good functional group compatibility and excellent chemoselectivity. The present work added highly polarized alkyl tosylate C—O bonds to the fairly limited number of C—O bonds able to participate in free radical cleavage pathways. The mechanistic studies suggested that in situ-generated silver(0) catalytic species were the active catalytic species and played a key role in the radical pathway cleavage of C—O bonds.
Complex Boron-Containing Molecules through a 1,2-Metalate Rearrangement/anti-SN2′ Elimination/Cycloaddition Reaction Sequence
Tillin, Chloe,Bigler, Raphael,Calo-Lapido, Renata,Collins, Beatrice S.L.,Noble, Adam,Aggarwal, Varinder K.
supporting information, p. 449 - 453 (2019/02/26)
The three-component coupling of benzylamines, boronic esters, and 4-phenyl-3 H -1,2,4-triazole-3,5(4 H)-dione (PTAD) is reported. The boronate complex formed from an ortho -lithiated benzylamine and a boronic ester undergoes a stereospecific 1,2-metalate rearrangement/ anti -S N 2′ elimination in the presence of an N-activator to provide a dearomatized tertiary boronic ester. Interception of this dearomatized intermediate with a dienophile leads to stereopredictable cycloaddition reactions to generate highly complex three-dimensional boron-containing molecular structures. When enantioenriched α-methyl-substituted benzylamines are employed, the corresponding cycloaddition adducts are formed with excellent enantiospecificities.
Cu-Catalyzed Decarboxylative Borylation
Wang, Jie,Shang, Ming,Lundberg, Helena,Feu, Karla S.,Hecker, Scott J.,Qin, Tian,Blackmond, Donna G.,Baran, Phil S.
, p. 9537 - 9542 (2018/09/27)
A simple method for the conversion of carboxylic acids to boronic esters via redox-active esters (RAEs) is reported using copper catalysis. The scope of this transformation is broad, and compared with the known protocols available, it represents the most inexpensive, rapid, and operationally simple option. In addition to a full exploration of the scope, a kinetic study was performed to elucidate substrate and reagent concentration dependences.
CU-AND NI-CATALYZED DECARBOXYLATIVE BORYLATION REACTIONS
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Page/Page column 44-45; 47-48; 51-53; 55, (2018/10/19)
The invention is directed to methods of converting a carboxylic acid group in a compound, via a redox active ester, to a corresponding boronic ester by treatment with bis(pinacolato)diboron-alkyllithium complex in the presence of a ligand, a Ni(ll) salt or a copper salt, and an Mg(ll) salt, in the presence of an alkyllithium or a lithium hydroxide or alkoxide salt. The product pinacolato boronate ester can be cleaved to provide a boronic acid. The invention is also directed to methods of preparing various compounds of medical value comprising boronic acid groups, and to novel boronic-acid containing compounds of medicinal value, including an atorvastatin boronic acid analog, a vancomycin aglycone boronic acid analog, and boronic acid containing elastase inhibitors mCBK319, mCBK320, mCBK323, and RPX-7009.
A method for preparing alkyl borate (by machine translation)
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Paragraph 0043; 0048; 0050, (2018/03/09)
The invention provides a method for preparing alkyl borate, comprises the following steps: formula I - a indicated by the alkyl tosylates and [...][...] as raw materials, in the silver catalyst and under the action of alkali, the reaction is carried out, as shown in formula I alkyl borate. The invention directly by adopting commercial silver salt as a catalyst in the reaction, the reaction system and feeding mode is simple, does not need to add ligand. The use [...][...] alcohol ester of the air and water are not sensitive, in practical application is more convenient. Alkyl tosylates raw material can be conveniently by alkyl alcohol preparation, raw material sources are extensive. At the same time, alkyl tosylates with [...][...] ester by a silver catalyzed direct carbon oxygen key fracture level or secondary alkyl borate, the reaction has good functional group compatibility. (by machine translation)
ortho-Directing Chromium Arene Complexes as Efficient Mediators for Enantiospecific C(sp2)–C(sp3) Cross-Coupling Reactions
Bigler, Raphael,Aggarwal, Varinder K.
supporting information, p. 1082 - 1086 (2018/01/10)
A new strategy for the coupling of a broad scope of electronically diverse aromatics to boronic esters is reported. The coupling sequence, which relies on the directed ortho-lithiation of chromium arene complexes followed by boronate formation and oxidation, occurs with complete ortho-selectivity and enantiospecificity to give the coupling products in excellent yields and with high functional group tolerance. An intermediate chromium arene boronate complex was characterized by X-ray, NMR, and IR experiments to elucidate the reaction mechanism.
α-Sulfinyl Benzoates as Precursors to Li and Mg Carbenoids for the Stereoselective Iterative Homologation of Boronic Esters
Casoni, Giorgia,Kucukdisli, Murat,Fordham, James M.,Burns, Matthew,Myers, Eddie L.,Aggarwal, Varinder K.
supporting information, p. 11877 - 11886 (2017/09/07)
The stereoselective reagent-controlled homologation of boronic esters is one of a small number of iteratable synthetic transformations that if automated could form the basis of a veritable molecule-making machine. Recently, α-stannyl triisopropylbenzoates and α-sulfinyl chlorides have emerged as useful building blocks for the iterative homologation of boronic esters. However, α-stannyl benzoates need to be prepared using stoichiometric amounts of the (+)- or (-)-enantiomer of the scarcely available and expensive diamine sparteine; also, these building blocks, together with the byproducts that are generated during homologation, are perceived as being toxic. On the other hand, α-sulfinyl chlorides are difficult to prepare with high levels of enantiopurity and are prone to undergo deleterious acid-base side-reactions under the reaction conditions for homologation, leading to low stereospecificity. Here, we show that the use of a hybrid of these two building blocks, namely, α-sulfinyl triisopropylbenzoates, largely overcomes the above drawbacks. Through either the sulfinylation of α-magnesiated benzoates with either enantiomer of Andersen's readily available menthol-derived sulfinate or the α-alkylation of enantiopure S-chiral α-sulfinyl benzoates, we have prepared a range of highly enantiopure mono- and disubstituted α-sulfinyl benzoates, some bearing sensitive functional groups. Barbier-type reaction conditions have been developed that allow these building blocks to be converted into lithium (t-BuLi) and magnesium (i-PrMgCl·LiCl) carbenoids in the presence of boronic esters, thus allowing efficient and highly stereospecific homologation. The use of magnesium carbenoids allows carbon chains to be grown with the incorporation of sensitive functional groups, such as alkyl/aryl halides, azides, and esters. The use of lithium carbenoids, which are less sensitive to steric hindrance, allows sterically encumbered carbon-carbon bonds to be forged. We have also shown that these building blocks can be used consecutively in three- and four-step iterative homologation processes, without intervening column chromatography, to give contiguously substituted carbon chains with very high levels of enantio- and diastereoselectivity.
Development of Enantiospecific Coupling of Secondary and Tertiary Boronic Esters with Aromatic Compounds
Odachowski, Marcin,Bonet, Amadeu,Essafi, Stephanie,Conti-Ramsden, Philip,Harvey, Jeremy N.,Leonori, Daniele,Aggarwal, Varinder K.
supporting information, p. 9521 - 9532 (2016/08/12)
The stereospecific cross-coupling of secondary boronic esters with sp2 electrophiles (Suzuki-Miyaura reaction) is a long-standing problem in synthesis, but progress has been achieved in specific cases using palladium catalysis. However, related couplings with tertiary boronic esters are not currently achievable. To address this general problem, we have focused on an alternative method exploiting the reactivity of a boronate complex formed between an aryl lithium and a boronic ester. We reasoned that subsequent addition of an oxidant or an electrophile would remove an electron from the aromatic ring or react in a Friedel-Crafts-type manner, respectively, generating a cationic species, which would trigger 1,2-migration of the boron substituent, creating the new C-C bond. Elimination (preceded by further oxidation in the former case) would result in rearomatization giving the coupled product stereospecifically. Initial work was examined with 2-furyllithium. Although the oxidants tested were unsuccessful, electrophiles, particularly NBS, enabled the coupling reaction to occur in good yield with a broad range of secondary and tertiary boronic esters, bearing different steric demands and functional groups (esters, azides, nitriles, alcohols, and ethers). The reaction also worked well with other electron-rich heteroaromatics and 6-membered ring aromatics provided they had donor groups in the meta position. Conditions were also found under which the B(pin)- moiety could be retained in the product, ortho to the boron substituent. This protocol, which created a new C(sp2)-C(sp3) and an adjacent C-B bond, was again applicable to a range of secondary and tertiary boronic esters. In all cases, the coupling reaction occurred with complete stereospecificity. Computational studies verified the competing processes involved and were in close agreement with the experimental observations.
Manganese-Catalyzed Borylation of Unactivated Alkyl Chlorides
Atack, Thomas C.,Cook, Silas P.
supporting information, p. 6139 - 6142 (2016/06/09)
The use of low-cost manganese(II) bromide (MnBr2) and tetramethylethylenediamine (TMEDA) catalyzes the cross coupling of (bis)pinacolatodiboron with a wide range of alkyl halides, demonstrating the first manganese-catalyzed coupling with alkyl electrophiles. This method allows access to primary, secondary, and tertiary boronic esters from the parent chlorides, which were previously inaccessible as coupling partners. The reaction proceeds in high yield with as little as 1000 ppm catalyst loading, while 5 mol % can provide high yields in as little as 30 min. Finally, radical-clock experiments revealed that at 0 °C direct borylation outcompetes alternative radical processes, thereby providing synthetically useful, temperature-controlled reaction outcomes.
Iron-catalyzed borylation of alkyl electrophiles
Atack, Thomas C.,Lecker, Rachel M.,Cook, Silas P.
supporting information, p. 9521 - 9523 (2014/07/22)
The use of low-cost iron(III) acetoacetate (Fe(acac)3) and tetramethylethylenediamine (TMEDA) enables the direct cross-coupling of alkyl halides with bis(pinacolato)diboron. This approach allows for the borylation of activated or unactivated primary, secondary, and tertiary bromides. Moreover, even the borylation of benzylic or allylic chlorides, tosylates, and mesylates are possible. The reactions proceed under mild conditions at room temperature and show broad functional-group compatibility and "robustness" as measured by a modified Glorius robustness screen.
