Selective oxidation of organoboranes with anhydrous trimethylamine N-oxide

Soderquist, John A.; Najafi, Meysam

doi:10.1021/jo00358a032

Cited by 100 publications

(46 citation statements)

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“…Thus, immersing samples of T-COF 1 through T-COF 4 in solutions of strong oxidizers such as 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and chloranyl produced dark materials, possibly indicative of charge transfer (CT) or even electron transport, but also induced amorphization of all of the T-COFs. We surmised that DDQ and chloranyl may oxidize the HOTP core itself or attack the oxidatively-prone B-C bond (29), both of which would explain the observed decomposition. Accordingly, we turned our attention to less potent oxidizers such as I 2 and TCNQ, the latter being a widely used electron acceptor in CT salts and complexes.…”

Section: Resultsmentioning

confidence: 99%

Thiophene-based covalent organic frameworks

Bertrand

Michaelis

Ong

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

301

205

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We report the synthesis and characterization of covalent organic frameworks (COFs) incorporating thiophene-based building blocks. We show that these are amenable to reticular synthesis, and that bent ditopic monomers, such as 2,5-thiophenediboronic acid, are defect-prone building blocks that are susceptible to synthetic variations during COF synthesis. The synthesis and characterization of an unusual charge transfer complex between thieno[3,2-b]thiophene-2,5-diboronic acid and tetracyanoquinodimethane enabled by the unique COF architecture is also presented. Together, these results delineate important synthetic advances toward the implementation of COFs in electronic devices.electronic materials | polymers | porous materials C ovalent organic frameworks (COFs) have emerged as an important class of polymeric crystalline materials with potential applications that complement those of metal organic frameworks (MOFs) (1-7). In particular, 2D COFs exhibit unique architectures wherein the monomers that make up their 2D layers stack almost perfectly into infinite 1D columns that are ideal for charge and exciton transport (6-12). Such electronic properties are particularly difficult to engineer in microporous MOFs, where high charge mobility and conductivity have only recently been demonstrated (13-15). Despite their layered structures, the typical hexagonal or square lattices of 2D COFs exhibit large 1D channels with well-defined pores that can be subject to reticular chemistry and postsynthetic modification (16,17), and where complementary donor or acceptor molecules may in principle be inserted. Clearly, the unprecedented combination of high surface area, crystallinity, chemical and pore size tunability, and unique molecular architecture make COFs tantalizing targets for a new generation of electronic devices, including sustainable batteries, field-effect transistors, and photovoltaics. The first steps toward such applications must involve the incorporation of electroactive monomers within the COFs. This has been beautifully exemplified by the insertion of porphyrins (18), phthalocyanines (9), pyrene (8), naphthalenetetracarboxydiimide (19), and benzothiadiazole (20) in such materials. Notably, however, one of the most popular monomers in conductive organic polymers, thiophene, has not been incorporated in COFs thus far. Herein, we report the synthesis and characterization of thiophene-based COFs, including materials made from thiophene-, bithiophene-, and thienothiophene-diboronic acids. We also advance a hypothesis regarding the more general synthetic tractability of COFs made from bent ligands. Finally, we show that p-type COFs are amenable to doping with electron acceptors and report an unusual charge-transfer complex with tetracyanoquinodimethane (TCNQ). Results and DiscussionWe prepared thiophene-based COF (T-COFs) under conditions mimicking those used for the synthesis of the prototypical COF-5. Thus, condensation of 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) with 2,5-thiophenediboronic acid (H 4 TDB) (21) in...

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Section: Resultsmentioning

confidence: 99%

Thiophene-based covalent organic frameworks

Bertrand

Michaelis

Ong

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

301

205

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“…37 For example, reaction of 2 mol equiv of trimethylamine N -oxide with 1 mol equiv of n -Bu 3 B is rapid. 45 However, reaction with the third molar equivalent of the N -oxide required 24 h at reflux. 45 On the basis of these results, we conducted several experiments.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Amine N-Oxides by Diboron Reagents

et al. 2011

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Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis(pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N-oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N’-dioxide of (S)-(–)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N-oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR.

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“…1,13 Compared to 1-alkynes, their 1-silyl counterparts also produce better yields of vinylboranes but, in contrast to normal internal alkynes, produce vicinal rather than geminal diboryl adducts with dihydroboration. 6,13, 14 Larger silyl groups can effectively be used to redirect the boron to the internal position producing the 'silyl-Markovnikov' vinylborane, exclusively, without competitive dihydroboration. 6 For 1-halo-1-alkynes, hydroboration with 9-BBN is slow, but the (Z)-1-halovinylboranes (eq 9) are produced cleanly and these are protonolyzed to provide cis-vinyl halides.…”

Section: %mentioning

confidence: 99%

9-Borabicyclo[3.3.1]nonane Dimer

Soderquist

Roush²,

Heo³

2004

Encyclopedia of Reagents for Organic Synthesis

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InChI = 1/2C8H15B/c2*1-3-7-5-2-6-8(4-1)9-7/h2*7-9H,1-6H2/ t2*7-,8+ InChIKey = FPEQNDQUWPJCKZ-MOGCCKQLBC (highly selective, stable hydroborating agent; 1,3 antiMarkovnikov hydration of alkenes and alkynes; 1d effective ligation for alkyl-, aryl-, allyl-, allenyl-, alkenyl-and alkynylboranes; 1a,4,5 forms stable dialkylboryl derivatives, borinate esters, and haloboranes; 1f organoboranes from hydroboration and organometallic reagents; 1,5 precursor to boracycles; 1,11 can selectively reduce conjugated enones to allylic alcohols; 1a,30 organoborane derivatives for α-alkylation and arylation of α-halo ketones, nitriles, and esters; 1b vinylation and alkynylation of carbonyl compounds; 1a,46 conjugate addition to enones; 1a,47 homologation; asymmetric reduction; Handling, Storage, and Precaution: the crystalline 9-BBN-H dimer can be handled in the atmosphere for brief periods without significant decomposition. However, the reagent should be stored under an inert atmosphere, preferably below 0 • C. Under these conditions the reagent is indefinitely stable. In solution, 9-BBN is more susceptible both to hydrolysis and oxidation, and contact with the open atmosphere should be rigorously avoided. Many 9-BBN derivatives are pyrophoric and/or susceptible to hydrolysis so that individuals planning to use 9-BBN-H dimer should thoroughly familiarize themselves with the special techniques required for the safe handling of such reagents prior to their use. 1b The reagent should be used in a well-ventilated hood.

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Selective oxidation of organoboranes with anhydrous trimethylamine N-oxide

Cited by 100 publications

References 0 publications

Thiophene-based covalent organic frameworks

Thiophene-based covalent organic frameworks

Reduction of Amine N-Oxides by Diboron Reagents

9-Borabicyclo[3.3.1]nonane Dimer

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