Synthesis, Characterization, and Functionalization of 1‐Boraphenalenes

Kahan, Rachel J.; Crossley, Daniel L.; Cid, Jessica; Radcliffe, James E.; Ingleson, Michael J.

doi:10.1002/ange.201803180

Cited by 27 publications

(5 citation statements)

References 59 publications

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“…For each synthesis, dehydrogenation was effected by reaction with a TEMPO radical solution at 80 °C for 24−36 h. Hydrolytic workup allowed the isolation of the desired polycyclic borinic acid products by silica gel chromatography (1−3, 5−6) or acidic aqueous extraction (4b). 1-Boraphenalene 1 (49%), 14 1,6-diborapyrene 2 (39%), 1,8-diborapyrene 3 (31%), 3,9-diboraperylene 4b (12%), 1,7-diboraanthanthrene 5 (22%), and 2,8-diboratriangulene 6 (15%) (Table 1) were characterized by multinuclear NMR spectroscopy and HRMS (see Supporting Information). Compounds 1−6 show no signs of degradation when stored as solids under ambient conditions for months.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Tunable Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbons by General One-Pot C–H Borylations

et al. 2019

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Boron-doping has long been recognized as a promising LUMO energy-lowering modification of graphene and related polycyclic aromatic hydrocarbons (PAHs). Unfortunately, synthetic difficulties have been a significant bottleneck for the understanding, optimization, and application of precisely boron-doped PAHs for optoelectronic purposes. Herein, a facile one-pot hydroboration electrophilic borylation cascade/dehydrogenation approach from simple alkene precursors is coupled with postsynthetic B-substitution to give access to ten ambient-stable core- and periphery-tuned boron-doped PAHs. These include large hitherto unknown doubly boron-doped analogues of anthanthrene and triangulene. Crystallographic, optical, electrochemical, and computational studies were performed to clarify the effect of boron-doped PAH shape, size, and structure on optoelectronic properties. Our molecular tuning allowed the synthesis of molecules exhibiting visible-range absorption, near-unity fluorescence quantum yields, and, to our knowledge, the most facile electrochemical reductions of any reported ambient-stable boron-doped PAHs (corresponding to LUMO energy levels as low as fullerenes). Finally, our study describes the first implementation of a precise three-coordinate boron-substituted PAH as an acceptor material in organic solar cells with power conversion efficiencies (PCEs) of up to 3%.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Tunable Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbons by General One-Pot C–H Borylations

et al. 2019

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“…We assign this as compound E (based on multinuclear NMR spectroscopy), with cis-haloboration based on an NOE experiment showing interaction between the vinylC-H and an aromatic C-H, with no other (trans-haloboration or 1,1-haloboration) isomers observed. 22,23 Previously, we have demonstrated that the addition of [BCl4] − salts can enhance the amount of the alkyne haloboration product formed in reactions where haloboration proceeds in competition with another transformation. 24 Presumably, the presence of [BCl4] − as an exogenous chloride source facilitates conversion of a vinyl cation to a vinyl chloride by chloride transfer.…”

Section: Resultsmentioning

confidence: 99%

trans-Haloboration of o-Alkynyl Phenols Generates Halogenated Bicyclic-Boronates Relevant to Broad Spectrum Beta-Lactamase Inhibitors

Yuan

Ingleson

2022

Preprint

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Benzoxaborinines are key intermediates on route to bicyclic boronates that are ultra-broad spectrum beta-lactamase inhibitors (BLIs). However, routes to benzoxaborinines are limited and substituents at C4 are not tolerated in the current key method. Herein, the haloboration of o-alkynyl-phenols using BX3 (X = Cl or Br) is disclosed as a simple route to form C4-halogenated benzoxaborinines. The functional group tolerance is excellent for an electrophilic borylation process, tolerating halides, ethers, esters, CF3 and an enolisable ketone. This methodology was extended to form benzoxaborinines with an ester at the C8 posi-tion (key for accessing highly active BLIs) in high yield by using BCl3 and [BCl4]−. The requirement for [BCl4]− as an exogenous chloride source indicated a switch in the haloboration mechanism and computational studies indicated that there are two similar in barrier mechanisms: (i) double alkyne haloboration followed by a retro-haloboration; (ii) concerted alkyne trans-haloboration with an exogenous chloride source ([BCl4]−). The C4-halide unit in these benzoxaborinines is useful, with a haloboration-Negishi cross coupling protocol used to form benzoxaborinines with an alkyl or an aryl group at C4. This simple trans-haloboration methodology represents a useful addition to the chemists toolbox for synthesizing bicyclic-boronates that are in-creasingly important active pharmaceutical ingredients.

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“…In situ NMR spectroscopy revealed that one other major product is formed which contained two boron centers, one three and one four coordinate (Figures S31 and S32). We assign this as compound D , with the cis ‐haloborated alkene isomer assigned based on NOE experiments, with no other haloboration isomers observed [24, 25] …”

Section: Figurementioning

confidence: 99%

Haloboration of o‐Alkynyl Phenols Generates Halogenated Bicyclic‐Boronates**

Kou

Ingleson

2023

Angew Chem Int Ed

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Benzoxaborinines are intermediates en-route to bicyclic boronates that are important active pharmaceutical ingredients (APIs). Herein, the haloboration of o-alkynyl-phenols using BX 3 (X = Cl or Br) is disclosed as a route to form C4-X-benzoxaborinines with good functional group tolerance. Computational studies indicated that there are two similar in barrier mechanisms: (i) double alkyne haloboration followed by retro-haloboration; (ii) concerted trans-haloboration involving an exogenous chloride source. The C4-halide in these benzoxaborinines is useful, with a one-pot haloboration-Negishi cross coupling protocol effective to form benzoxaborinines with an alkyl or an aryl at C4. Therefore this method is a useful addition to the toolbox for synthesising bicyclic-boronates that are attracting increasing attention as APIs.

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Synthesis, Characterization, and Functionalization of 1‐Boraphenalenes

Cited by 27 publications

References 59 publications

Tunable Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbons by General One-Pot C–H Borylations

Tunable Low-LUMO Boron-Doped Polycyclic Aromatic Hydrocarbons by General One-Pot C–H Borylations

trans-Haloboration of o-Alkynyl Phenols Generates Halogenated Bicyclic-Boronates Relevant to Broad Spectrum Beta-Lactamase Inhibitors

Haloboration of o‐Alkynyl Phenols Generates Halogenated Bicyclic‐Boronates**

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