Towards a monomeric structure of phenylboronic acid: The influence of ortho-alkoxy substituents on the crystal structure

Cyrański, Michał K.; Klimentowska, Paulina; Rydzewska, Agata; Serwatowski, Janusz; Sporzyński, Andrzej; Stępień, Dorota K.

doi:10.1039/c2ce25657f

Cited by 34 publications

(23 citation statements)

References 43 publications

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“…The structure of 1g was confirmed by the X‐ray analysis (Figure 1). It is interesting to note that in one of two crystallographically independent molecules 1g ‐A, the B(OH) 2 group bound to the C3 atom adopts a rarely observed anti – anti conformation 7. Both of the molecular structures (i.e., 1g ‐A and 1g ‐B) are stabilized by intramolecular OH ··· Br hydrogen bonds (geometrical details are given in Table 1S in the Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

The Influence of Boronate Groups on the Selectivity of the Br–Li Exchange in Model Dibromoaryl Boronates

Durka¹,

Luliński²,

Smętek³

et al. 2013

Eur J Org Chem

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The selectivity of the Br/Li exchange reaction of 6‐butyl‐2‐(2,5‐dibromophenyl)‐1,3,6,2‐dioxazaborocane (2,5‐Br2C6H3B(OCH2CH2)2NBu) and the analogous anionic derivatives, 2,5‐Br2C6H3B(OiPr)3Li and 2,5‐Br2C6H3BF3K, was investigated using nBuLi as the lithiating reagent. In the case of the former compound there was a slight preference for lithiation at the 5‐position. For 2,5‐Br2C6H3B(OiPr)3Li, the lithiation occured exclusively at C5, but for 2,5‐Br2C6H3BF3K, 2‐lithiation was preferred. Calculations performed for the lithiation of ortho‐ and meta‐brominated phenyl boronates revealed that ortho‐lithiated aryl boronates are thermodynamically more stable, but that the Br/Li exchange is generally dictated by kinetics, which accounts for the variation of selectivity depending on the type of boronate group. In addition, the successful generation of the 2,5‐dilithiophenyl boronate species 2,5‐Li2C6H3B(OCH2CH2)2NBu by a double Br/Li interconversion is reported. The Br/Li exchange in the related 6‐butyl‐2‐[3‐(2,5‐dibromothienyl)]‐1,3,6,2‐dioxazaborocane, 2,5‐Br2‐3‐ThB(OCH2CH2)2NBu, occured preferentially at the 5‐position, but the product was readily transformed into the more stable 2‐lithiated isomer. The use of 2 equiv. of nBuLi resulted in the efficient formation of the dilithiated species, 2,5‐Li2‐3‐ThB(OCH2CH2)2NBu. The obtained lithiated aryl boronates were converted into functionalized arylboronic acids by treatment with selected electrophiles.

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Section: Resultsmentioning

confidence: 99%

The Influence of Boronate Groups on the Selectivity of the Br–Li Exchange in Model Dibromoaryl Boronates

Durka¹,

Luliński²,

Smętek³

et al. 2013

Eur J Org Chem

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“…Breaking of the dimer motif is possible due to intramolecular hydrogen bond formation. 37 The -B(OH) 2 groups adopt the most preferred syn−anti conformation in the salt of 5 and 7, while they adopt relatively uncommon syn−syn conformation in the salt of 6. 33 In the present case of 6, both -B(OH) 2 functions have syn−syn orientation, with the consequence that the water molecules act as hydrogen-bonding donors within the molecule.…”

Section: Crystal Structure Of [4-pbah] 2 [Pdcl 4 ] (4)mentioning

confidence: 99%

Chlorometallate-Pyridinium Boronic Acid Salts for Crystal Engineering: Synthesis of One-, Two-, and Three-Dimensional Hydrogen Bond Networks

Yahşi

Güngör

Kara

2015

Crystal Growth & Design

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A series of new crystal structures of salts containing 3-and 4-pyridineboronic acid (3-and 4-pba) with chlorometallate have been prepared: [4-pbaH][MnCl 2 ] (1), [4-pbaH][CdCl 2 ], (2), [4-pbaH] 2 [CuCl 4 ] (3), [4-pbaH] 2 [PdCl 4 ] (4), [3-pbaH] 2 [CdCl 4 ] (5), [3-pbaH][CuCl 3 (OH 2 )] (6), and [3-pbaH][PdCl 2 ] (7). In these salts five structural forms for the chlorometallate species are observed: mononuclear square planar [M = Pd (4 and 7)], dimeric square-pyramidal [M = Cu (3)], polymeric square-pyramidal [M = Cu (6)], polymeric trans-edge-sharing octahedral [M = Mn (1), Cd (2)], and polymeric cis-edge-sharing octahedral [M = Cd (5)]. The cyclic R2,2(8) boronic acid dimer is formed in the salt of 1−5. NH···Cl 2 M synthons A have been exploited in 1−4, 6, and 7. Both NH···Cl 2 M (sythons A) and B(OH) 2 ···Cl 2 M (sythons B) interactions give rise to a synthon of form I in 6. The uncommon folded conformation of the NH···Cl 2 M (synthons A) are formed in 7. The NH or OH donors and consequent branching of the NH···Cl hydrogen-bond network leads to one-, two-, and three-dimensional structures. These structures are further stabilized by CH···O and CH···Cl and π···π stacking interactions. ■ INTRODUCTIONRecently, boronic acids and its derivatives have attracted a great deal of attention due to their properties and applications in the areas of pharmaceuticals, agrochemicals, 1−3 and in medicine as antibiotics, 4−6 antibody mimics for polysaccharides, 7,8 for the development of enzyme inhibitors like protease inhibitors, 9−14 boron neutron capture (BNCT) therapy agents, 15−19 and for the treatment of tumors. 20 In the area of organic chemistry, boronic acid derivatives have also been widely used in cross-coupling reactions, 1 carboxylic acid activation, 21,22 and as reagents and starting materials in organic synthesis. 23 Therefore, this functional group has been recently used as a new building block in crystal engineering and also has been of current interest in supramolecular chemistry with respect to hydrogen-bonded derivatives. 24−31 In supramolecular synthesis, boronic acids, with general formula R−B(OH) 2 , have been well considered to be potential cocrystal formers, 29−39 due to the flexibility of the -B(OH) 2 functional group which enables the formation of a variety of hydrogen bonded assemblies in one-or multicomponent systems. 40−43 It is known from the literature that the presence of two hydroxyl groups of boronic acids leads to form mainly three types of conformations, identified as syn−anti, syn−syn, and anti−anti, 44,45 as shown in Scheme 1, which yield different hydrogen-bonding networks. Among these arrangements, while syn−anti conformation is observed in a majority of structures, the syn−syn and anti−anti conformations are relatively uncommon. 33,46 However, it is interesting to note that the hydroxyl groups are arranged in a syn−syn conformation in 6.Orpens and co-workers reported a range of charge-assisted hydrogen-bond acceptor tectons such as anionic [PtCl 4 ] 2− , with cationic, often pyridinium...

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“…The reaction is affected not only by the character of the substituents, but also by their position: the presence of the ortho substituents related to the boronic group has been reported to increase the deboronation rate . This effect is connected with intramolecular interactions, especially hydrogen bonding …”

Section: Introductionmentioning

confidence: 99%

Fluorinated Boronic Acids: Acidity and Hydrolytic Stability of Fluorinated Phenylboronic Acids

et al. 2017

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Abstract:The acidity constants and hydrolytic stability of all isomers of fluoro-substituted phenylboronic acids (F 1 -F 5 ) have been determined by both spectrophotometric and potentiometric methods. The introduction of fluorine into the aromatic ring enhances the Lewis acidity of boronic acids, depending on the position and number of fluorine substituents. Results of both methods show good agreement in most of the cases. To explain the observed discrepancies for several compounds, sta-

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Towards a monomeric structure of phenylboronic acid: The influence of ortho-alkoxy substituents on the crystal structure

Cited by 34 publications

References 43 publications

The Influence of Boronate Groups on the Selectivity of the Br–Li Exchange in Model Dibromoaryl Boronates

The Influence of Boronate Groups on the Selectivity of the Br–Li Exchange in Model Dibromoaryl Boronates

Chlorometallate-Pyridinium Boronic Acid Salts for Crystal Engineering: Synthesis of One-, Two-, and Three-Dimensional Hydrogen Bond Networks

Fluorinated Boronic Acids: Acidity and Hydrolytic Stability of Fluorinated Phenylboronic Acids

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