7294-50-0Relevant articles and documents
Reaction of B2(o-tol)4 with CO and Isocyanides: Cleavage of the C≡O Triple Bond and Direct C?H Borylations
Katsuma, Yuhei,Tsukahara, Nana,Wu, Linlin,Lin, Zhenyang,Yamashita, Makoto
, p. 6109 - 6114 (2018)
The reaction of highly Lewis acidic tetra(o-tolyl)diborane(4) with CO afforded a mixture of boraindane and boroxine by the cleavage of the C≡O triple bond. 13C labeling experiments confirmed that the carbon atom in the boraindane stems from CO. Simultaneously, formation of boroxine 3 could be considered as borylene transfer to capture the oxygen atom from CO. The reaction of diborane(4) with tBu?NC afforded an azaallene, while the reaction with Xyl?NC furnished cyclic compounds by direct C?H borylations.
Nickel(II)-Catalyzed Addition of Aryl and Heteroaryl Boroxines to the Sulfinylamine Reagent TrNSO: The Catalytic Synthesis of Sulfinamides, Sulfonimidamides, and Primary Sulfonamides
Lo, Pui Kin Tony,Willis, Michael C.
supporting information, p. 15576 - 15581 (2021/10/02)
We report a redox-neutral Ni(II)-catalyzed addition of (hetero)aryl boroxines to N-sulfinyltritylamine (TrNSO). The reactions use a catalyst generated from the combination of commercial, air-stable NiCl2·(glyme) and a commercially available bipyridine lig
Redox-Neutral ortho Functionalization of Aryl Boroxines via Palladium/Norbornene Cooperative Catalysis
Li, Renhe,Liu, Feipeng,Dong, Guangbin
supporting information, p. 929 - 939 (2019/04/10)
Palladium/norbornene (Pd/NBE) cooperative catalysis, also known as the Catellani reaction, has become an increasingly useful method for site-selective arene functionalization; however, certain constraints still exist because of its intrinsic mechanistic pathway. Herein, we report a redox-neutral ortho functionalization of aryl boroxines via Pd/NBE catalysis. An electrophile, such as carboxylic acid anhydrides or O-benzoyl hydroxylamines, is coupled at the boroxine ortho position, and a proton as the second electrophile is introduced at the ipso position. This reaction does not require extra oxidants or reductants and avoids stoichiometric bases or acids, thereby tolerating a wide range of functional groups. In particular, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated, which could be used to control reaction sequences. Finally, a deuterium-labeling study supports the ipso protonation pathway. This unique mechanistic feature could inspire the development of a new class of Pd/NBE-catalyzed transformations.Poly-substituted aromatics are ubiquitously found in drugs and agrochemicals. To realize streamlined synthesis, it is highly attractive if functional groups can be site-selectively introduced at unactivated positions with common arene starting materials. Here, a method is developed to directly introduce acyl and amino groups at unactivated ortho positions of readily available aryl boron compounds. Compared with the known ortho functionalization approaches, this method does not require stoichiometric bases, external oxidants, or reductants. Consequently, the reaction is chemoselective: a wide range of functional groups, including highly reactive aryl iodides, can be tolerated. The primary innovation lies in the use of a proton to terminate the ipso aryl intermediate and regenerate the active palladium catalyst. This unique mode of reactivity in the palladium/norbornene catalysis should open the door for developing new redox-neutral methods for site-selective arene functionalization.A redox-neutral ortho functionalization of aryl boroxines via palladium/norbornene cooperative catalysis is developed. The ortho amination and acylation are achieved with carboxylic acid anhydrides and O-benzoyl hydroxylamines as an electrophile, respectively, whereas protonation occurs at the ipso position. This transformation avoids using either extra oxidants and reductants or stoichiometric bases and acids. In addition, orthogonal chemoselectivity between aryl iodide and boroxine moieties is demonstrated for pathway divergence.
Rhodium-Catalyzed Enantioposition-Selective Hydroarylation of Divinylphosphine Oxides with Aryl Boroxines
Wang, Zhe,Hayashi, Tamio
supporting information, p. 1702 - 1706 (2018/02/06)
The rhodium-catalyzed hydroarylation of divinylphosphine oxides (RP(O)(CH=CH2)2) with aryl boroxines ((ArBO)3) gives the corresponding monoarylation products (RP(O)(CH=CHAr)CH2CH3) in high yields. One of the two vinyl groups in the phosphine oxide undergoes oxidative arylation while the other one is reduced to an ethyl moiety. These reactions proceed with high selectivity in terms of the enantiotopic vinyl groups in the presence of (R)-DTBM-segphos/Rh to give the P-stereogenic monoarylation products with high enantioselectivity.
Unveiling the role of boroxines in metal-free carbon-carbon homologations using diazo compounds and boronic acids
Bomio, Claudio,Kabeshov, Mikhail A.,Lit, Arthur R.,Lau, Shing-Hing,Ehlert, Janna,Battilocchio, Claudio,Ley, Steven V.
, p. 6071 - 6075 (2017/08/29)
By means of computational and experimental mechanistic studies the fundamental role of boroxines in the reaction between diazo compounds and boronic acids was elucidated. Consequently, a selective metal-free carbon-carbon homologation of aryl and vinyl boroxines using TMSCHN2, giving access to TMS-pinacol boronic ester products, was developed.
Enantiodivergent Fluorination of Allylic Alcohols: Data Set Design Reveals Structural Interplay between Achiral Directing Group and Chiral Anion
Neel, Andrew J.,Milo, Anat,Sigman, Matthew S.,Toste, F. Dean
supporting information, p. 3863 - 3875 (2016/04/09)
Enantioselectivity values represent relative rate measurements that are sensitive to the structural features of the substrates and catalysts interacting to produce them. Therefore, well-designed enantioselectivity data sets are information rich and can provide key insights regarding specific molecular interactions. However, if the mechanism for enantioselection varies throughout a data set, these values cannot be easily compared. This premise, which is the crux of free energy relationships, exposes a challenging issue of identifying mechanistic breaks within multivariate correlations. Herein, we describe an approach to addressing this problem in the context of a chiral phosphoric acid catalyzed fluorination of allylic alcohols using aryl boronic acids as transient directing groups. By designing a data set in which both the phosphoric and boronic acid structures were systematically varied, key enantioselectivity outliers were identified and analyzed. A mechanistic study was executed to reveal the structural origins of these outliers, which was consistent with the presence of several mechanistic regimes within the data set. While 2- and 4-substituted aryl boronic acids favored the (R)-enantiomer with most of the studied catalysts, meta-alkoxy substituted aryl boronic acids resulted in the (S)-enantiomer when used in combination with certain (R)-phosphoric acids. We propose that this selectivity reversal is the result of a lone pair-π interaction between the substrate ligated boronic acid and the phosphate. On the basis of this proposal, a catalyst system was identified, capable of producing either enantiomer in high enantioselectivity (77% (R)-2 to 92% (S)-2) using the same chiral catalyst by subtly changing the structure of the achiral boronic acid.
Palladium(II)-Catalyzed Enantioselective Synthesis of α-(Trifluoromethyl)arylmethylamines
Johnson, Thomas,Luo, Bo,Lautens, Mark
, p. 4923 - 4930 (2016/07/06)
We describe a method for the synthesis of α-(trifluoromethyl)arylmethylamines that consists of the palladium(II)-catalyzed addition of arylboroxines to imines derived from trifluoroacetaldehyde. Palladium acetate is used as a catalyst with electron-neutral or electron-rich arylboroxines, and it was found that addition of an ammonium or silver salt was crucial to promote the reaction of electron-poor boroxines. With (S)-t-Bu-PyOX as the chiral ligand, this method delivers a variety of α-trifluoromethylated amines in 57-91% yield and with greater than 92% ee in most cases.
Rhodium-Catalyzed Asymmetric Arylation/Defluorination of 1-(Trifluoromethyl)alkenes Forming Enantioenriched 1,1-Difluoroalkenes
Huang, Yinhua,Hayashi, Tamio
supporting information, p. 12340 - 12343 (2016/10/07)
The reaction of 1-(trifluoromethyl)alkenes (CF3CH=CHR) with arylboroxines (ArBO)3 in the presence of a chiral diene-rhodium catalyst gave high yields of chiral 1,1-difluoroalkenes (CF2=CHC?HArR) with high enantioselectivity (≥95% ee). The reaction is assumed to proceed through β-fluoride elimination of a β,β,β-trifluoroalkylrhodium intermediate that is generated by arylrhodation of the 1-(trifluoromethyl)alkene.
Oxidative coupling of aryl boron reagents with sp3-carbon nucleophiles: The enolate chan–evans–lam reaction
Moon, Patrick J.,Halperin, Heather M.,Lundgren, Rylan J.
supporting information, p. 1894 - 1898 (2016/12/03)
Reported is a versatile new oxidative method for the arylation of activated methylene species. Under mild reaction conditions (RT to 40°C), Cu(OTf)2mediates the selective coupling of functionalized aryl boron species with a variety of stabilized sp3-nucleophiles. Tertiary malonates and amido esters can be employed as substrates to generate quaternary centers. Complementing either traditional cross-coupling or SNAr protocols, the transformation is chemoselective in the presence of halogen electrophiles, including aryl bromides and iodides. Substrates bearing amide, sulfonyl, and phosphonyl groups, which are not amenable to coupling under mild Hurtley-type conditions, are suitable reaction partners.
Oxidative Heck desymmetrisation of 2,2-disubstituted cyclopentene-1,3-diones
Walker,Lamb,Beattie,Nikodemiak,Lee
supporting information, p. 4089 - 4092 (2015/03/30)
Oxidative Heck couplings have been successfully developed for 2,2-disubstituted cyclopentene-1,3-diones. The direct coupling onto the 2,2-disubstituted cyclopentene-1,3-dione core provides a novel expedient way of enantioselectively desymmetrising all-carbon quaternary centres. This journal is
