- Mild metal-free syn-stereoselective ring opening of activated epoxides and aziridines with aryl borates
-
A conceptually new, simple and practical method for the syn-nucleophilic displacement of aryl and vinyl epoxides and aryl aziridines with (substituted) phenols, using aryl borates as activating nucleophiles under neutral conditions, is reported. The Royal Society of Chemistry 2005.
- Pineschi, Mauro,Bertolini, Ferruccio,Haak, Robert M.,Crotti, Paolo,Macchia, Franco
-
-
Read Online
- The Nature of meso - And pyro -Borate Precatalysts to the VANOL and VAPOL BOROX Catalysts
-
The structures of the meso- and pyro-borate esters generated by treatment of the VANOL and VAPOL ligands with triphenylborate have been revisited. These species were previously identified as precatalysts that could be in situ converted into VANOL and VAPOL BOROX catalysts by an imine substrate. The complete assignment of all protons for both the meso- and pyro-borate esters of both ligands was aided by the 1H NMR spectrum of each generated from pentadeuterophenol. There were significant differences between the chemical shifts for certain protons in the meso- and pyro-borate species in both the VANOL and VAPOL derivatives. Optimized structures for the meso-borates and two different isomers of the pyro-borates were determined by DFT calculations for each ligand. For each ligand the cyclic pyro-borate was found to be lower in energy than the corresponding linear pyro-borate at the B3LYP/6-311+G(d,p) level of theory. The structures of the cyclic pyro-borate esters were more consistent with the observed 1H NMR chemical shifts than the linear pyro-borates for each ligand and thus the structures of the pyro-borates esters of VANOL and VAPOL have been re-assigned as the cyclic isomers.
- Zhao, Wenjun,Yin, Xiaopeng,Gupta, Anil K.,Zhang, Xin,Wulff, William D.
-
-
Read Online
- Reaction of triphenyl borate with 1,3,5-trioxane
-
Triphenyl borate was prepared by reaction of boric acid with phenol in xylene. Its reaction with 1,3,5-trioxane involved replacement of protons in the para positions of the benzene rings by methylene group.
- Lenskii,Shul'Ts,Androshchuk,Tolstikov
-
-
Read Online
- Facile and reliable synthesis of tetraphenoxyborates and their properties
-
Tetraphenoxyborates are reliably prepared in a two-step sequence, exploiting less corrosive reagents like boric acid and the corresponding phenols. The broad scope of this transformation is demonstrated in 22 examples. Several solid-state structures reveal the preferential conformation of the phenoxy moieties allowing cation interaction. Furthermore, a novel architecture of a phenoxy-substituted tetraborate was found. Surprisingly, the tetraphenoxyborates exhibit a good stability in neutral and basic media. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Malkowsky, Itamar M.,Frohlich, Roland,Griesbach, Ulrich,Puetter, Hermann,Waldvogel, Siegfried R.
-
-
Read Online
- Pyro-Borates, Spiro-Borates, and Boroxinates of BINOL - Assembly, Structures, and Reactivity
-
VANOL and VAPOL ligands are known to react with three equivalents of B(OPh)3 to form a catalytic species that contains a boroxinate core with three boron atoms, and these have proven to be effective catalysts for a number of reactions. However, it was not known whether the closely related BINOL ligand will likewise form a boroxinate species. It had simply been observed that mixtures of BINOL and B(OPh)3 were very poor catalysts compared to the same mixtures with VANOL or VAPOL. Borate esters of BINOL have been investigated as chiral catalysts, and these include meso-borates, spiro-borates, and diborabicyclo-borate esters. Borate esters are often in equilibrium, and their structures can be determined by stoichiometry and/or thermodynamics, especially in the presence of a base. The present study examines the structures of borate esters of BINOL that are produced with different stoichiometric combinations of BINOL with B(OPh)3 in the presence and absence of a base. Depending on conditions, pyro-borates, spiro-borates, and boroxinate species can be generated and their effectiveness in a catalytic asymmetric aziridination was evaluated. The finding is that BINOL borate species are not necessarily inferior catalysts to those of VANOL and VAPOL but that, under the conditions, BINOL forms two different catalytic species (a boroxinate and a spiro-borate) that give opposite asymmetric inductions. However, many BINOL derivatives with substitutents in the 3- and 3′-positions gave only the boroxinate species and the 3,3′-Ph2BINOL ligand gave a boroxinate catalyst that gives excellent inductions in the aziridination reaction. BINOL derivatives with larger groups in the 3,3′-position will not form either spiro-borates or boroxinate species and thus are not effective catalysts at all.
- Hu, Gang,Gupta, Anil K.,Huang, Li,Zhao, Wenjun,Yin, Xiaopeng,Osminski, Wynter E. G.,Huang, Rui H.,Wulff, William D.,Izzo, Joseph A.,Vetticatt, Mathew J.
-
supporting information
p. 10267 - 10285
(2017/08/09)
-
- Industrial synthesis method for salicylaldehyde
-
The invention discloses an industrial synthesis method for salicylaldehyde and relates to the technical field of organic synthesis. The method comprises the steps of putting phenol, o-chlorotoluene and boric acid into an esterifying reactor, carrying out a reaction while controlling the reaction temperature to be below 80 DEG C, transferring the material into a hydroformylation reactor after the esterifying reaction ends, then, slowly adding paraformaldehyde into the hydroformylation reactor, carrying out a reaction while controlling the reaction temperature to be below 90 DEG C, carrying out natural cooling after the hydroformylation reaction ends, adding a sodium hydroxide solution for neutralization when the temperature is dropped to 20 DEG C, adding a catalyst after the neutralization ends, introducing air, then, adding concentrated sulfuric acid for oxidation-acidification reactions, and finally, carrying out distilling separation, thereby obtaining a finished product, i.e., the salicylaldehyde. According to the method, the loss of intermediate products and production workload are reduced, the volume of wastewater produced is low, the raw materials are cheap and readily available, and the prepared salicylaldehyde product is high in purity and can be used for synthesizing a variety of chemicals as a raw material.
- -
-
Paragraph 0017; 0018
(2017/09/02)
-
- Synthesis and antioxidant characteristics of borate esters used in lubricating oil
-
In the present studies, the preparation of esters of boric acid with hindered phenols is reported, wherein the alkyl groups are branched on the α-carbon atoms. The products were evaluated in terms of their oxidative stability. In most cases, improvements in oxidative stability in ahydrocarbon media (cumene) were observed.
- Shekarriz,Ghanbari,Taghipoor,Khalili,Hajialiakbari,Adibi,Soleymani
-
experimental part
p. 3646 - 3652
(2010/11/04)
-
- Substrate-induced covalent assembly of a chemzyme and crystallographic characterization of a chemzyme-substrate complex
-
A substrate induced covalent assembly of a highly organized chemzyme known to be effective in both catalytic asymmetric aziridination and aza Diels-Alder reactions is described and the information gained from which led to an efficient one-pot aziridination protocol. The crystal structures of two chemzyme-iminium complexes were elucidated by X-ray diffraction analysis that provides critical insights into the binding of the substrates with the chemzyme.
- Hu, Gang,Gupta, Anil K.,Huang, Rui H.,Mukherjee, Munmun,Wulff, William D.
-
supporting information; experimental part
p. 14669 - 14675
(2010/12/25)
-
- Regio- and stereoselective ring opening of enantiomerically enriched 2-aryl oxetanes and 2-aryl azetidines with aryl borates
-
(Chemical Equation Presented) The regioselective ring opening of 2-aryl-substituted four-membered heterocyclic rings with phenols, including catechol, was achieved by the use of aryl borates in mild and neutral reaction conditions without the aid of any transition metal catalysts. While β-alkyl azetidines were found not to be reactive, optically active N-tosyl azetidines gave the corresponding β-aryloxy amines in a racemic form, thus indicating the considerable carbocationic character of the transition state. The introduction of a hydroxyl group in the azetidine ring (i.e., an azetidinol), able to anchor the aryl borate and to direct the subsequent nucleophilic delivery, was shown to determine the ring-opening process with predominant inversion of configuration. When enantiomerically enriched 2-aryl oxetanes were used, the reduced extent of racemization observed (up to 93:7 er) was rationalized by an intramolecular delivery through a six-membered transition state, giving β-aryloxy alcohols with a predominant retention of configuration (i.e., a syn-stereoselective ring opening). The aryloxy alcohols obtained, endowed with suitable functionalities, can be cyclized to give access to enantiomerically enriched 2-aryl-1,5-benzodioxepins.
- Bertolini, Ferruccio,Crotti, Stefano,Di Bussolo, Valeria,Macchia, Franco,Pineschi, Mauro
-
supporting information; experimental part
p. 8998 - 9007
(2009/04/11)
-
- Contribution to the Chemistry of Boron, 224 Reactions and Structure of Electron-Precise Triborane(5) and Tetraborane(6) Derivatives
-
An improved synthesis of B3(NMe2)5 (2), B4(NMe2)6 (1), and B6(NMe2)8 (4) is reported.From each compound two of the four terminal dimethylamino groups are readily replaced by halogen atoms yielding α,ω-dihalides Bn(NMe2)nX2 (n = 3, 4; X = Cl, Br, I).These are used in turn to replace the substituent X by groups like RO, RS, RHN, R2P, and R.Crystal structure determinations on several of these compounds reveal as a common feature planar (C2N)BB2 and (C2N)B(B)X groups which are arranged in an approximately orthogonal manner to one another with NBBN dihedral angles ranging from 69 to 104.6 deg.Consequently, there is no significant ? bonding between the boron atoms. - Key Words: Triboranes(5), 1,ω-disubstituted / Tetraboranes(6), 1,ω-disubstituted / Hexaborane(8), octakis(dimethylamino)- / Electron-precise polyboranes
- Linti, Gerald,Loderer, Dirk,Noeth, Heinrich,Polborn, Kurt,Rattay, Wilfried
-
p. 1909 - 1922
(2007/10/02)
-
- Preparation of phenylalkyl ethers and phenyl esters from benzenediazonium tetrafluoroborate with alkoxytrimethylsilanes and trimethylsilyl esters
-
Sonication assisted reaction of benzenediazonium tetrafluoroborate with alkoxytrimethylsilanes and trimethylsilyl esters gives phenylalkyl ethers and phenyl esters, respectively, with trialkyl(aryl) borates as byproducts. The scope of the reaction, experimental conditions and proposed mechanism are discussed.
- Olah,Wu
-
p. 204 - 206
(2007/10/02)
-
- Contributions to the Chemistry of Boron, 161. Reactions of Protic Reagents with (tert-Butylimino)(2,2,6,6-tetramethylpiperidino)borane
-
The aminoiminoborane 2 adds protic reagents of type HX (X=OH, OR, OCOR, SH, SR, NH2, NHR, NHNR2) across the formal BN triple bond regiospecifically forming (tert-butylamino)(2,2,6,6-tetramethylpiperidino)boranes (3-7, 12, 13, 15, 16a, b, 17-27) which are inert towards ligand redistribution.The relative rates of addition are primarily governed by steric factors (NH3 > NH2R > HNR2; HOR > HSR >HNR2).Bulky amines HNR2 will not add to 2.Excess HX (X=OH, OR, OC(O)R)reacts with the boranes formed on 1:1 addition by breaking BN bonds; however, no prediction can be made concerning which BN bond in tmpBX will be cleaved.
- Brandl, Andreas,Noeth, Heinrich
-
p. 3759 - 3770
(2007/10/02)
-
- Addition compounds of alkali-metal hydrides. 24. A general method for preparation of potassium trialkoxyborohydrides. A new class of reducing agents
-
The generality of the synthesis of potassium triisopropoxyborohydride, stabilized toward disproportionation by storing over excess potassium hydride, was examined with seven additional organoborates of varying steric requirements. The reaction of trimethoxy- and triethoxyborane with potassium hydride proceeded readily at room temperature, but the products could not be stabilized by the presence of excess potassium hydride. Triphenoxyborane reacted readily, even at -10°C, and stabilization was achieved. Tri-sec-butoxy- and tricyclopentoxyborane required refluxing in THF for 12-24 h, and the products were stabilized over potassium hydride. Finally, the reactions of tris(2-methylcyclohexoxy)- and tri-tert-butoxyborane were even slower, requiring a number of days for completion. Both products were stabilized toward disproportionation over potassium hydride. Indeed, potassium tri-tert-butoxyborohydride was quite stable toward disproportionation without excess potassium hydride. The stereoselectivities of these reagents in the reduction of representative cyclic ketones were examined. The stereoselectivities varied in an erratic manner with the steric requirements of the alkoxy group and did not approach the stereoselectivities previously achieved with lithium tri-sec-butylborohydride and lithium trisiamylborohydride.
- Brown, Herbert C.,Cha, Jin Soon,Nazer, Behrooz
-
p. 2929 - 2931
(2008/10/08)
-
- Catalytic hydrocyanation of olefins by nickel(0) phosphite complexes - Effects of Lewis acids
-
Mechanistic studies on the addition of HCN to olefins using Ni[P(O-o-tolyl)3]3 catalyst show that the reactions proceed under mild conditions via (η1-organo)- or (η3-organo)nickel cyanide intermediates formed by the insertion of monoenes or dienes into the nickel-hydrogen bond of HNiL3CN. The RNiLmCN intermediates can be identified spectroscopically by NMR and IR in some cases. In the case of very electronegative R groups (formed for example from reactions of HNiL3CN with C2F4 or acrylonitrile), reductive elimination does not occur, and the catalyst is poisoned for olefin hydrocyanation. Improved rates, catalyst lifetimes, and product linearity can be obtained by the addition of Lewis acid (A) cocatalysts. Spectroscopic studies show that Lewis acids can coordinate strongly to the nitrogen lone-electron pair of hydrido cyanide intermediates to form HNiL3CN-A complexes. An explanation of the effects of Lewis acids on hydrocyanation is proposed, which involves increasing the concentration of nickel in catalytic loop species [in the P(O-p-tolyl)3 system], accelerating the rate of carbon-carbon coup ing to form alkanenitriles from alkylnickel cyanide complexes and destabilizing relatively bulky branched alkyl intermediates relative to less crowded linear ones.
- Tolman,Seidel,Druliner,Domaille
-
-
- Process for preparing aldehydes from oxirane compounds
-
Aldehydes are prepared by reacting an oxirane compound with hydrogen peroxide in the presence of a boron compound.
- -
-
-
