H-Bond Acceptor Parameters for Anions

Pike, Sarah J.; Hutchinson, Jordan; Hunter, Christopher A.

doi:10.1021/jacs.7b02008

Cited by 134 publications

(123 citation statements)

References 61 publications

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“…For DT2–DT5 , binding to Cl − was found to be very weak ( K a <12 m −1 in all cases), but stronger binding was observed to the oxoanions with binding affinities decreasing across the series H 2 PO 4 − >AcO − >BzO − . This trend does not correlate with the basicity of the anions, in direct contrast to previous observations for the urea and squaramide compound series, nor does it correlate with the recently reported hydrogen bond acceptor parameter series, in which carboxylates are shown to be stronger hydrogen bond acceptors than − O 2 P(OR) 2 …”

Section: Resultsmentioning

confidence: 99%

Deltamides and Croconamides: Expanding the Range of Dual H‐bond Donors for Selective Anion Recognition

Zwicker

Yuen

Smith

et al. 2017

Chemistry A European J

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Dual H-bond donors are widely used as recognition motifs in anion receptors. We report the synthesis of a library of dual H-bond receptors, incorporating the deltic and croconic acid derivatives, termed deltamides and croconamides, respectively, and a comparison of their anion binding affinities (for monovalent species) and Brønsted acidities to those of the well-established urea and squaramide dual H-bond donor motifs. For dual H-bonding cores with identical substituents, the trend in Brønsted acidity is croconamides>squaramides>deltamides>ureas, with the croconamides found to be 10-15 pK units more acidic than the corresponding ureas. In contrast to the trends displayed by ureas, deltamides and squaramides, N,N'-dialkyl croconamides displayed higher binding affinity to chloride than the N,N'-diaryl derivatives, which was attributed to partial deprotonation of the N,N'-diaryl derivatives at neutral pH. A number of differences in anion binding selectivity were observed upon comparison of the dual H-bond cores. Whereas the squaramides display similar affinity for both chloride and acetate ions, the ureas have significantly higher affinity for acetate than chloride ions and the deltamides display higher affinity for dihydrogenphosphate ions than other oxoanions or halides. These inherent differences in binding affinity could be exploited in the design of anion receptors with improved ability to discriminate between monovalent anions.

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Section: Resultsmentioning

confidence: 99%

Deltamides and Croconamides: Expanding the Range of Dual H‐bond Donors for Selective Anion Recognition

Zwicker

Yuen

Smith

et al. 2017

Chemistry A European J

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“…When IL/2 ratio changes from 2 to 4, reduction of the yields of 5 and 6 is usually observed, probably owing to their further fluorination forming 8 and 9 (Scheme 3). It was found that the rate of formation of products 5, 6, 8 and 9 at lower temperature while using hydrophilic ionic liquids [ 22 The change of the cation part of IL has a small influence on the yield of fluorides ( Table 4). The results clearly show that total yields poorly correlate with the polarity of ionic liquids.…”

Section: Resultsmentioning

confidence: 99%

Promotional effect of ionic liquids in electrophilic fluorination of phenols

Borodkin¹,

Elanov²,

Shubin³

et al. 2017

Arkivoc

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The influence of a stoichiometric amount of ionic liquids (IL) on the fluorination of phenols in various solvents has been studied. The fluorination of phenol, 1-naphthol and resorcinol was carried out using 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F-TEDA-BF 4 , Selectfluor™) with the formation of 2-fluoro-, 4-fluorophenol, 2-fluoro-, 4-fluoronaphthol and 4-fluoro-, 4,6-difluoro-benzene-1,3-diol as the main products. The use of a stoichiometric amount of ionic liquid as an additive results in acceleration of the reactions. The effect is most significant at low temperatures. It has been found that solvent polarity has an essential effect on the difference in yields of fluoroproducts obtained in the presence of IL and without it.

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“…NMR titrations showed that even in polar MeCN,s ignificant association is seen. [16] Background titrations of 5,5'-dimethylbipyridine against 2h showed negligible interaction, demonstrating that the sulfonate group is responsible for the observed shifts of the N-H proton. Finally, N-alkylated substrates resulted in poor regioselectivity upon borylation with ligand 1a,e mphasizing the importance of the N À Hinorder to achieve high levels of regiocontrol and providing support for the crucial role of hydrogen bonding (Figure 3d).…”

Section: Angewandte Chemiementioning

confidence: 95%

meta‐Selective C−H Borylation of Benzylamine‐, Phenethylamine‐, and Phenylpropylamine‐Derived Amides Enabled by a Single Anionic Ligand

2017

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Selective functionalization at the meta position of arenes remains as ignificant challenge.I nt his work, we demonstrate that as ingle anionic bipyridine ligand bearing ar emote sulfonate group enables selective iridium-catalyzed borylation of ar ange of common amine-containing aromatic molecules at the arene meta position. We propose that this selectivity is the result of ak ey hydrogen bonding interaction between the substrate and catalyst. The scope of this metaselective borylation is demonstrated on amides derived from benzylamines,p henethylamines and phenylpropylamines; amine-containing building blocks of great utility in many applications.The employment of non-covalent interactions to direct transition metal catalysis is as trategy of great potential but remains relatively underexplored, particularly for addressing issues of regioselectivity and site-selectivity. [1,2] Ac ommonly encountered regioselectivity choice arises during the functionalization of aromatic rings.I ne lectrophilic aromatic substitution, regioselectivity is determined largely by the electronic predisposition of the substrate,w hile proximity to adirecting group is the determining factor in directed orthometalation chemistry and many catalytic arene CÀHf unctionalizations.[3] Thea pplication of C À Hf unctionalization strategies to distal positions is more challenging [4,5] and we believe that the design of catalytic systems which incorporate attractive non-covalent interactions constitutes ap owerful strategy to address these challenges.[1c]Iridium-catalyzed CÀHb orylation has evolved into au niquely powerful arene functionalization method that operates under mild conditions,ishighly tolerant of functionality and delivers boronate esters that can be readily transformed into av ariety of common groups.[6] Perhaps most interesting is the regioselectivity of this process,w hich is largely controlled by steric considerations. [6a,7] Whilst highly effective for borylation of 1,3-disubstituted arenes,i someric mixtures are typically obtained when borylation is applied to monosubstituted and unsymmetrical 1,2-disubstituted arenes, limiting broader application. There have been an umber of developments in ortho-selective borylation, [8,9] but much fewer achieve meta- [10] or para-selectivity.[11] Thep roductive harnessing of non-covalent interactions has played ac rucial role in several recent advances. [9i, 11b] This includes "outer sphere" hydrogen bond-directed approaches such as those developed by Singleton, Maleczka, Smith and co-workers for ortho-borylation of aniline derivatives [9d,e] (Figure 1a)and by Kuninobu, Kanai and co-workers for meta-selective borylation of arenes bearing carbonyl and phosphoryl groups (Figure 1b).[10a] We have recently disclosed ab ipyridine ligand bearing ad istal anionic sulfonate group to direct iridium-catalyzed borylation to the arene meta position in two classes of aromatic quaternary ammonium salts,b yv irtue of aputative ion-pairing interaction between the active catalyst and cationic sub...

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H-Bond Acceptor Parameters for Anions

Cited by 134 publications

References 61 publications

Deltamides and Croconamides: Expanding the Range of Dual H‐bond Donors for Selective Anion Recognition

Deltamides and Croconamides: Expanding the Range of Dual H‐bond Donors for Selective Anion Recognition

Promotional effect of ionic liquids in electrophilic fluorination of phenols

meta‐Selective C−H Borylation of Benzylamine‐, Phenethylamine‐, and Phenylpropylamine‐Derived Amides Enabled by a Single Anionic Ligand

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