Organoboron Compounds. II. The Reducing Action of Some Organoboronic Acids<sup>1</sup>

Johnson, John R.; Campen, M. G. Van; Grummitt, Oliver

doi:10.1021/ja01268a034

Cited by 59 publications

(24 citation statements)

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“…It had been shown that aromatic boronic acids react with silver(I) salts in ammoniacal solution to form the corresponding arene, boric acid and Ag 2 O. [94] The higher conversion of para-tolylboronic acid into toluene in the presence of pyridine suggested thus that a pyridine-silver(I) complex is likely involved, in the same way, in the homolytic deboronation of para-tolylboronic acid and this complex is degraded to pyridine and inactive Ag 2 O. The use of an additive capable of preventing the formation of this catalytically inactive Ag 2 O, such as HNO 3 , allowed the isolation of 2-tolyl-4-trifluoromethylpyridine in an excellent 90% yield (vs. 76% with Barans conditions), with only 10 mol% AgNO 3 and 2 equivalents of K 2 S 2 O 8.…”

Section: Manganesea C H T U N G T R E N N U N G (Iii) and Used For Thmentioning

confidence: 99%

“…Almost 60 % of para ‐tolylboronic acid was converted into toluene in the presence of pyridine, whereas the conversion decreased to 15% only in the absence of pyridine. It had been shown that aromatic boronic acids react with silver(I) salts in ammoniacal solution to form the corresponding arene, boric acid and Ag 2 O 94. The higher conversion of para ‐tolylboronic acid into toluene in the presence of pyridine suggested thus that a pyridine‐silver(I) complex is likely involved, in the same way, in the homolytic deboronation of para ‐tolylboronic acid and this complex is degraded to pyridine and inactive Ag 2 O.…”

Section: Generation Of Aryl Radicals Using An Oxidantmentioning

confidence: 99%

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Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

2014

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This review gives an overview of the generation of aryl radicals, mediated by transition metals, and their use for the C À H arylation of heteroarenes. The different sources of aromatic derivatives able to generate aryl radicals via a metal-assisted reduction or oxidation are discussed, with a critical view of the developed systems. The radical arylations of nitrogen-, oxygen-or sulfur-containing heterocycles are then described and mechanistic considerations are discussed as well.

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Section: Manganesea C H T U N G T R E N N U N G (Iii) and Used For Thmentioning

confidence: 99%

Section: Generation Of Aryl Radicals Using An Oxidantmentioning

confidence: 99%

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

2014

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“…Although amides are minor reaction products, their formation from the corresponding boronates is quite often observed in basic aqueous solutions. [25] In detail, the coupling reaction between carboxylic acids 13 and pinanediol leucine boronate (14) led to the formation of amides 5 obtained by spontaneous deboronation of boronic esters 15 (Scheme 2).…”

Section: Chemistrymentioning

confidence: 99%

Development of Novel Selective Peptidomimetics Containing a Boronic Acid Moiety, Targeting the 20S Proteasome as Anticancer Agents

et al. 2014

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This paper describes the design, synthesis, and biological evaluation of peptidomimetic boronates as inhibitors of the 20S proteasome, a validated target in the treatment of multiple myeloma. The synthesized compounds showed a good inhibitory profile against the ChT-L activity of 20S proteasome. Compounds bearing a β-alanine residue at the P2 position were the most active, that is, 3-ethylphenylamino and 4-methoxyphenylamino (R)-1-{3-[4-(substituted)-2-oxopyridin-1(2H)-yl]propanamido}-3-methylbutylboronic acids (3 c and 3 d, respectively), and these derivatives showed inhibition constants (Ki ) of 17 and 20 nM, respectively. In addition, they co-inhibited post glutamyl peptide hydrolase activity (3 c, Ki=2.57 μM; 3 d, Ki=3.81 μM). No inhibition was recorded against the bovine pancreatic α-chymotrypsin, which thus confirms the selectivity towards the target enzyme. Docking studies of 3 c and related inhibitors into the yeast proteasome revealed the structural basis for specificity. The evaluation of growth inhibitory effects against 60 human tumor cell lines was performed at the US National Cancer Institute. Among the selected compounds, 3 c showed 50% growth inhibition (GI50) values at the sub-micromolar level on all cell lines.

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“…15c,g Starting from the stable cyclic sulfone 3a 17 it was possible to synthesize the bi-and terthiophene sulfones 3b and 3c via Suzuki coupling 18 of the respective bromo derivatives 4a , b (Table1) with 2-thienylboronic acid. 19 To improve the solubility of higher oligothienylfullerenes it was necessary to introduce pentyl groups into the oligothiophene as shown in Scheme 3.…”

Section: Biographical Sketchesmentioning

confidence: 99%

Synthesis of Oligothienylfullerenes

Effenberger¹,

Grube²

1998

Synthesis

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Donor-acceptor substituted α -oligothiophenes with anthracene as donor and C 60 -fullerene as acceptor were synthesized via [4+2]-cycloaddition of C 60 -fullerene with the heteroanalogous o -quinodimethanes of anthryloligothiophenes. The o -quinodimethanes were generated in situ by cheletropic extrusion of SO 2 of the corresponding cyclic sulfones. The oligothienosulfones have been prepared successively starting from 4,6-dihydrothieno[3,4-b ]thiophene 5,5-dioxide via brominations and metal-catalyzed Suzuki coupling reactions. Several oligothienylfullerenes without anthracene as terminal group have been synthesized in the same way."Supermolecules" which consist of various molecular subunits play an important role for studying photochemical and photophysical processes. The photosynthesis is one example in nature, where the transformation of light energy into chemical energy occurs in a "supermolecule". The synthesis of model compounds and investigations of their optical and electrical properties for possible applications as devices for information transfer and storage at a molecular level, is a great challenge for chemists and physicists alike. In the present publication syntheses of model compounds consisting of subunits for a photoinduced intramolecular electron transfer are described.In terminally donor-acceptor substituted conjugated polyenes a nearly quantitative intramolecular energy transfer from the excited donor to the acceptor could be shown. 2 An interruption of this energy transfer through insertion of a saturated spacer fails, which can be explained by Förster energy transfer. 3 Substitution of the polyene chain by oligothiophenes in these energy transfer systems led to an improvement of the selectivity of excitation but most importantly to a drastic increase of quantum yields. 4a An interruption of the energy transfer in these molecules by introduction of saturated spacers into the oligothiophene chain also fails. 4bAs a result of these investigations, an interruption or switching of energy transfer in this type of compounds seems to be not possible. We have therefore developed and investigated similar compounds for an intramolecular electron transfer. The described model compounds for an energy transfer had to be varied in such a way, that they are suitable for an intramolecular electron transfer. For that reason the terminal porphyrin group was substituted by a pyridinium group as acceptor. 5 A photoexcited electron transfer in these compounds could be proved by transient absorption of the anthryl radical cation. 5b The proof of a pyridine radical, however, fails. 5bIt was therefore the aim of this work to synthesize terminally donor-acceptor substituted oligothiophenes with anthracene as donor and C 60 -fullerene as acceptor. In case of an intramolecular electron transfer the experimental proof of fullerene radical anion besides the anthryl radical cation should be possible.Fullerenes have a moderate electron affinity, which has been shown by theoretical studies 6a as well as by electrochemical mea...

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Organoboron Compounds. II. The Reducing Action of Some Organoboronic Acids¹

Cited by 59 publications

References 0 publications

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

Development of Novel Selective Peptidomimetics Containing a Boronic Acid Moiety, Targeting the 20S Proteasome as Anticancer Agents

Synthesis of Oligothienylfullerenes

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Organoboron Compounds. II. The Reducing Action of Some Organoboronic Acids1

Cited by 59 publications

References 0 publications

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

Transition Metal‐Mediated Direct CH Arylation of Heteroarenes Involving Aryl Radicals

Development of Novel Selective Peptidomimetics Containing a Boronic Acid Moiety, Targeting the 20S Proteasome as Anticancer Agents

Synthesis of Oligothienylfullerenes

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Organoboron Compounds. II. The Reducing Action of Some Organoboronic Acids¹