5747-23-9Relevant academic research and scientific papers
Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworks
Spitler, Eric L.,Dichtel, William R.
, p. 672 - 677 (2010)
Covalent organic frameworks (COFs) offer a new strategy for assembling organic semiconductors into robust networks with atomic precision and long-range order. General methods for COF synthesis will allow complex building blocks to be incorporated into these emerging materials. Here we report a new Lewis acid-catalysed protocol to form boronate esters directly from protected catechols and arylboronic acids. This transformation also provides crystalline boronate ester-linked COFs from protected polyfunctional catechols and bis(boronic acids). Using this method, we prepared a new COF that features a square lattice composed of phthalocyanine macrocycles joined by phenylene bis(boronic acid) linkers. The phthalocyanines stack in an eclipsed fashion within the COF to form 2.3 n pores that run parallel to the stacked chromophores. The material's broad absorbance over the solar spectrum, potential for efficient charge transport through the stacked phthalocyanines, good thermal stability and the modular nature of COF synthesis, show strong promise for applications in organic photovoltaic devices.
Activation of Aryl Carboxylic Acids by Diboron Reagents towards Nickel-Catalyzed Direct Decarbonylative Borylation
Deng, Xi,Guo, Jiandong,Su, Weiping,Wang, Xiaotai,Zhang, Xiaofeng
supporting information, p. 24510 - 24518 (2021/08/12)
The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B2cat2 has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non-ortho-substituted (hetero)aryl carboxylic acids, and tolerates diverse functional groups including some of the groups active to Ni0 catalysts. The key to achieve this decarbonylative borylation reaction is the choice of B2cat2 as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates aryl carboxylic acids towards oxidative addition of their C(acyl)?O bond to Ni0 catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted decarbonylation and reductive elimination step that generates the aryl boronic ester product. This mode of boron-promoted carboxylic acid activation is also applicable to other types of reactions.
Formation of a hydride containing amido-zincate using pinacolborane
Ingleson, Michael J.,Nichol, Gary S.,Uzelac, Marina,Yuan, Kang
supporting information, p. 14018 - 14026 (2021/10/19)
Amido-zincates containing hydrides are underexplored yet potentially useful complexes. Attempts to access this type of zincate through combining amido-organo zincates and pinacolborane (HBPin)viaZn-C/H-BPin exchange led instead to preferential formation of amide-BPin and/or [amide-BPin(Y)]?(Y = Ph, amide, H), when the amide is hexamethyldisilazide or 2,2,6,6-tetramethylpiperidide and the hydrocarbyl group was phenyl or ethyl. In contrast, the use of a dipyridylamide (dpa) based arylzinc complex led to Zn-C/H-BPin metathesis being the major outcome. Independent synthesis and full characterisation of two LnLi[(dpa)ZnPh2] (L = THF,n= 3; L = PMDETA,n= 1) complexes,1and3, respectively, enabled reactivity studies that demonstrated that these species display zincate type reactivity (by comparison to the lower reactivity of the neutral complex (Me-dpa)ZnPh2,4, Me-dpa = 2,2′-dipyridyl-N-methylamine). This included1performing the rapid deprotonation of 4-ethynyltoluene and also phenyl transfer to α,α,α-trifluoroacetophenone in contrast to neutral complex4. Complex1reacted with one equivalent of HBPin to give predominantly PhBPin (ca.90%) and a lithium amidophenylzincate containing a hydride unit, complex7-A, as the major zinc containing product. Complex7-Atransfers hydride to an electrophile preferentially over phenyl, indicating it reacts as a hydridozincate. Attempts to react1with >1 equivalent of HBPin or with catecholborane led to more complex outcomes, which included significant borane and dpaZn substituent scrambling, two examples of which were crystallographically characterised. While this work provides proof of principle for Zn-C/H-BPin exchange as a route to form an amido-zincate containing a hydride, amido-organozincates that undergo more selective Zn-C/H-BPin exchange still are required.
Synthesis of Boroxine and Dioxaborole Covalent Organic Frameworks via Transesterification and Metathesis of Pinacol Boronates
Hamzehpoor, Ehsan,Jonderian, Antranik,McCalla, Eric,Perepichka, Dmitrii F.
, p. 13274 - 13280 (2021/09/07)
Boroxine and dioxaborole are the first and some of the most studied synthons of covalent organic frameworks (COFs). Despite their wide application in the design of functional COFs over the last 15 years, their synthesis still relies on the original Yaghi's condensation of boronic acids (with itself or with polyfunctional catechols), some of which are difficult to prepare, poorly soluble, or unstable in the presence of water. Here, we propose a new synthetic approach to boroxine COFs (on the basis of the transesterification of pinacol aryl boronates (aryl-Bpins) with methyl boronic acid (MBA) and dioxaborole COFs (through the metathesis of pinacol boronates with MBA-protected catechols). The aryl-Bpin and MBA-protected catechols are easy to purify, highly soluble, and bench-stable. Furthermore, the kinetic analysis of the two model reactions reveals high reversibility (Keq ~1) and facile control over the equilibrium. Unlike the conventional condensation, which forms water as a byproduct, the byproduct of the metathesis (MBA pinacolate) allows for easy kinetic measurements of the COF formation by conventional 1H NMR. We show the generality of this approach by the synthesis of seven known boroxine/dioxaborole COFs whose crystallinity is better or equal to those reported by conventional condensation. We also apply metathesis polymerization to obtain two new COFs, Py4THB and B2HHTP, whose synthesis was previously precluded by the insolubility and hydrolytic instability, respectively, of the boronic acid precursors.
Electronic Spectroscopy of 2-Phenyl-1,3,2-benzodioxaborole and Its Derivatives: Important Building Blocks of Covalent Organic Frameworks
Jimenez-Hoyos, Carlos A.,Knee, Joseph L.,Northrop, Brian H.,Ryan, Roberta P.,Savino, Cara
, p. 529 - 537 (2020/02/25)
Aryl boronate esters, such as 2-phenyl-1,3,2-benzodioxaborole (1), are important components in the formation of a variety of covalent organic frameworks. The addition of substituents on the aromatic rings of aryl boronate esters has the potential to modif
Isodesmic C-H Borylation: Perspectives and Proof of Concept of Transfer Borylation Catalysis
Rochette, étienne,Desrosiers, Vincent,Soltani, Yashar,Fontaine, Frédéric-Georges
supporting information, p. 12305 - 12311 (2019/08/20)
The potential advantages of using arylboronic esters as boron sources in C-H borylation are discussed. The concept is showcased using commercially available 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes using arylboronates as borylation agents. The catalysis shows a unique functional group tolerance among C-H borylation reactions, tolerating notably terminal alkene and alkyne functional groups. The mechanistic investigation is also described.
Mechanism and Scope of Nickel-Catalyzed Decarbonylative Borylation of Carboxylic Acid Fluorides
Malapit, Christian A.,Bour, James R.,Laursen, Simon R.,Sanford, Melanie S.
supporting information, p. 17322 - 17330 (2019/11/03)
This Article describes the development of a base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester products. Detailed studies were conducted to assess the relative rates of direct transmetalation between aryl boronate esters and diboron reagents and a bisphosphine nickel(aryl)(fluoride) intermediate. These investigations revealed that diboron reagents undergo transmetalation with this Ni(aryl)(fluoride) intermediate at rates significantly faster than their aryl boronate ester congeners. Furthermore, the reactivity of both boron reagents toward transmetalation is enhanced with increasing electrophilicity of the boron center. These mechanistic insights were leveraged to develop a catalytic decarbonylative borylation of acid fluorides that proved applicable to a variety of (hetero)aryl carboxylic acid fluorides as well as diverse diboron reagents. The acid fluorides can be generated in situ directly from carboxylic acids. Furthermore, the mechanistic studies directed the identification of various air-stable Ni pre-catalysts for this transformation.
Self-Assembly of Fluorinated Boronic Esters and 4,4′-Bipyridine into 2:1 N→B Adducts and Inclusion of Aromatic Guest Molecules in the Solid State: Application for the Separation of o, m, p -Xylene
Campillo-Alvarado, Gonzalo,Vargas-Olvera, Eva C.,H?pfl, Herbert,Herrera-Espa?a, Angel D.,Sánchez-Guadarrama, Obdulia,Morales-Rojas, Hugo,Macgillivray, Leonard R.,Rodríguez-Molina, Braulio,Farfán, Norberto
, p. 2726 - 2743 (2018/05/09)
A series of 2:1 fluorinated arylboronic ester adducts with 4,4′-bipyridine sustained by N→B dative bonds have been synthesized. The degree of fluorination in the arylboronic esters derived from catechol is shown to modulate the molecular conformation of t
Metal-Free Radical Borylation of Alkyl and Aryl Iodides
Cheng, Ying,Mück-Lichtenfeld, Christian,Studer, Armido
, p. 16832 - 16836 (2018/11/23)
A metal-free radical borylation of alkyl and aryl iodides with bis(catecholato)diboron (B2cat2) as the boron source under mild conditions is introduced. The borylation reaction is operationally easy to conduct and shows high functional group tolerance and broad substrate scope. Radical clock experiments and density functional theory calculations provide insights into the mechanism and rate constants for C-radical borylation with B2cat2 are disclosed.
Bench-Stable Sulfoxide-Based Boronates: Preparation and Application in a Tandem Suzuki Reaction
?ubiňák, Marek,Eigner, Václav,Tobrman, Tomá?
supporting information, p. 4604 - 4614 (2018/10/31)
A set of novel aromatic and heteroaromatic bench-stable sulfoxide-based boronates was prepared. The structure of the boronates was established by means of X-ray crystallography, and the prepared boronates were successively used in Suzuki cross-coupling reactions under different conditions. We also developed a tandem Suzuki reaction so that a base is generated during the nucleophilic addition of Grignard reagents to 4-bromobenzaldehyde. The formed intermediates were smoothly coupled with the prepared boronates and the boronic acids under external base-free conditions. (Figure presented.).
