Borinic acid, also known asboronous acid, is an oxyacid ofboron with formulaH 2BOH.Borinate is the associated anion of borinic acid with formulaH 2BO− ; however, being aLewis acid, the form in basic solution isH 2B(OH)− 2. Borinic acids (containing RR'BOH) and borinic esters (RR'BOR") also refer to the families of compounds derived from the parent by replacing hydrogen atoms with more generalorganyl groups. Their primary application is in academic research.
TheIUPAC nameborinic acid is a unique name for the acid.[1] The anhydrides are named diboroxanes, H2BOBH2, as the base compound and H being able to be substituted, e.g. tetraethyldiboroxane, as the anhydride for diethylborinic acid. Organic naming standard in theBluebook allows skeletal replacement naming where the name is shorter, 3-borapentan-3-ol versus diethyl borinic acid. The grouping -BH-O-BH2 is called diboroxanyl. Substituting sulfur for oxygen gives borinothioic acid (H2BSH). (Dimethylboranyl)oxy is used for the group (CH3)2B-O− and methyl(hydroxy)boranyl for the grouping CH3B(OH)-.
Borinic acid itself is unstable and only lasts for a few seconds during the hydrolysis reaction. However, by using microwave spectroscopy various properties can be determined. The B-O distance is 1.352 Å, O-H distance 0.96 Å, B-H length is probably 1.2 Å. The angle between bonds at the oxygen atom BOH = 112° and the angles at boron are cis-HBO 121°, and trans-HBO = 117°. The dipole moment is 1.506Debye.[3]
Borinic acid can form esters such as methoxyborane. This too is unstable only lasting about ten seconds. It can be formed by heatingdiborane andmethanol gas together.[4]
There are several ways to produce substituted borinic acids.[5]
Firstly borinic acids can be made from oxidizingtrialkylborane starting materials (R3B) with exposure to moist air, or treatment with iodine, which makes a dialkyliodoborane (R2BI). Hydrolysis then results in the boronic acid (R2BOH).[5] Dialkyl boron chloride (R2BCl) with tertiary amine react with ketones to form an enol borinate.[6] Suchalcoholysis products require purification, as often boronic esters will also be produced and mixed in with the borinic esters.[5] The method ofLetsinger is to dissolve the mixture in ether and precipitate the borinic ester as an ammonia complex. Treatment withethanolamine ends up making an aminoethylborinate.[5]
Secondly, trialkylborates [(RO)3B] or trialkoxyboroxine [(ROBO)3] can be reduced to borinic acid by us of aGrignard reagent. Grignard reagents can also reduce a boronic ester [RB(OR')2] to a borinic ester.[5]
Likewise, a trialkoxyborane can react with lithium containing organic molecules to eliminate lithium and one or two alkoxy groups to make boronic and borinic esters.[7]
and same fortBu2PCH2C(CF3)2OB(C6F5)2[8] di-Tris(tert-butoxy)siloxy borinic acid HOB[OSi(O(t)Bu)3]2 can be made from tributoxyborate and tributoxysiloxane. It can form a very complex crystal with Cp2Zr(Me)[OB[OSi(O(t)Bu)3]2]2.[9]
A wide variety of borinic acids, anhydrides ((R2B)2O), and esters (R2BOR′) are known.[10][11] Diborinic acids have two RBOH groups linked together by an organic connection such as diphenyl or phenyl.[12]
Besides those below, other compounds include methoxy(dimethyl)borane, methoxy(methyl)boron, methoxy(methylidene)borane (with a C=B double bond).[13]
2-Aminoethoxydiphenyl borate (2-APB) inhibitstransient receptor potential channels.[14] This kind of inhibition, particularly inhibition ofTRPM7, is being studied to find treatments forprostate cancer. 2-APB can work as a catalyst to add an alkyl group from an alkyl halide to a polyol or carbohydrate that contains a cis-vicinal diol to a precise position. It does this by first combining with the two hydroxy groups to make a ring containing OCCOB−.[15] It can also calatlyse acid chloride or chloroformate reaction a specific region of the diol.[16]
Diphenylborinic acid was discovered in 1894 by Michaelis who produced it by hydrolyzing the chloride. Letsinger determined its properties in 1955.[5] Diphenylborinic acid can catalyse the condensation ofpyruvic acids withaldehydes to yield substitutedisotetronic acid.[17] Diphenylborinic acid has an extra high affinity for catechols compared with carbohydrates.[18]
Esters will tend to be stable in acidic conditions, but in alkaline conditions the boron atom can gain a negative charge and attach two hydroxyl groups, or two ester bonds. RR'B−(OH)2 or RR'B−(OR")2. The anionic borinate ion can very easily form esters withdiols such asethylene glycol or sugars.[citation needed]
Borinate radicals (RR'BO·) can be formed from peroxyborinate decomposition.[20]
Chiral boronates enol esters are applied in academia for enantioselectivealdol reactions. (Z)-Enolates givesyn products, whereas (E)-enolates giveanti products.[citation needed]
1,1,1,3,3,3-Hexafluoroisopropylbis(pentafluorophenyl)borinate can greatly increase solubility of LiF by complexing the F− anion.[21]
Borinic esters are being researched as bacterial growth inhibitors[22] due to their ability to disable some bacterial enzymes such asmenaquinone methyltransferase andCcrM.[23]
^Connelly, Neil G.; Damhus, Ture; Hartshorn, Richard M.; Alan T. Hutton (2005). "Table IR-8.1 Acceptable common names".Nomenclature of Inorganic Chemistry. International Union of Pure and Applied Chemistry. p. 127.ISBN0-85404-438-8.
^Weiss, H. G.; Shapiro, I. (5 March 1953). "Mechanism of the Hydrolysis of Diborane in the Vapor Phase1".Journal of the American Chemical Society.75 (5):1221–1224.Bibcode:1953JAChS..75.1221W.doi:10.1021/ja01101a061.
^Kawashima, Yoshiyuki; Takeo, Harutoshi; Matsumura, Chi (1 January 1981). "Microwave spectrum of borinic acid BH2OH".The Journal of Chemical Physics.74 (10): 5430.Bibcode:1981JChPh..74.5430K.doi:10.1063/1.440947.
^Chapman, Andy M.; Haddow, Mairi F.; Orton, Jonathan P. H.; Wass, Duncan F. (1 January 2010). "Facile dihydrogen release from phosphino-borinate ester Lewis pairs".Dalton Transactions.39 (27):6184–6.doi:10.1039/c0dt00513d.PMID20544115.
^Fujdala, KL; Oliver, A. G.; Hollander, F. J.; Tilley, T. D. (Feb 24, 2003). "Tris(tert-butoxy)siloxy derivatives of boron, including the boronous acid HOB[OSi(O(t)Bu)(3)](2) and the metal (siloxy)boryloxide complex Cp(2)Zr(Me)OB[OSi(O(t)Bu)(3)](2): a remarkable crystal structure with 18 independent molecules in its asymmetric unit".Inorganic Chemistry.42 (4):1140–1150.doi:10.1021/ic0205482.PMID12588150.
^US Abandoned 20020161230, Erbes, Michael; Forstinger, Klaus & Meudt, Andreas, "Process for preparing boronic and borinic acids", published 31 Oct 2002, assigned to Clariant GmbH
^Chan, Lina; Taylor, Mark S. (17 June 2011). "Regioselective Alkylation of Carbohydrate Derivatives Catalyzed by a Diarylborinic Acid Derivative".Organic Letters.13 (12):3090–3093.doi:10.1021/ol200990e.PMID21591630.
^Lee, Doris; Taylor, Mark S. (23 March 2011). "Borinic Acid-Catalyzed Regioselective Acylation of Carbohydrate Derivatives".Journal of the American Chemical Society.133 (11):3724–3727.Bibcode:2011JAChS.133.3724L.doi:10.1021/ja110332r.PMID21355584.
^Lee, Doris; Newman, Stephen G.; Taylor, Mark S. (3 December 2009). "Boron-Catalyzed Direct Aldol Reactions of Pyruvic Acids".Organic Letters.11 (23):5486–5489.doi:10.1021/ol902322r.PMID19904926.
^Chudzinski, Michael G.; Chi, Yuechuan; Taylor, Mark S. (1 January 2011). "Borinic Acids: A Neglected Class of Organoboron Compounds for Recognition of Diols in Aqueous Solution".Australian Journal of Chemistry.64 (11): 1466.doi:10.1071/CH11294.
^Steiner, Steven J.; Bien, Jeffrey T.; Smith, Bradley D. (1 October 1994). "Diphenylborinic acid is a strong inhibitor of serine proteases".Bioorganic & Medicinal Chemistry Letters.4 (20):2417–2420.doi:10.1016/S0960-894X(01)80401-7.
^Benkovic SJ, Baker SJ, Alley MR, Woo YH, Zhang YK, Akama T, Mao W, Baboval J, Rajagopalan PT, Wall M, Kahng LS, Tavassoli A, Shapiro L (1 November 2005). "Identification of Borinic Esters as Inhibitors of Bacterial Cell Growth and Bacterial Methyltransferases, CcrM and MenH".Journal of Medicinal Chemistry.48 (23):7468–7476.doi:10.1021/jm050676a.PMID16279806.
Dimitrijević, Elena; Taylor, Mark S. (3 May 2013). "Organoboron Acids and Their Derivatives as Catalysts for Organic Synthesis".ACS Catalysis.3 (5):945–962.doi:10.1021/cs4000848. Review of use borinic acids as a catalyst
