Diisopropyl borate

Solutions of 7.5 g (40 mmol) of triisopropyl borate in 10 mL of dry diethyl ether and 40 mmol of 0.87 M allylmagnesium bromide in diethyl ether arc added dropwisc separately to 10 mL of diethyl ether at — 78 °C. This mixture is stirred for 0.5 h at —78 JC, then is allowed to warm to r.t. and stirred for 3 h. The slurry is recooled to 0 C. and then 40 mmol or 1 N aq hydrochloric acid saturated with NaCl are added dropwise over 15 min. The mixture is warmed to r.t., and stirring is continued for 10 min. The organic layer is separated and directly treated with 9.4 g (40 mmol) of diisopropyl (/ ,/ )-tartrate (DIPT). The aqueous phase is extracted with three 50-mL portions of diethyl elher/CH.CI, 5 1. The combined organic layers are dried over anhyd MgS04 for 2.5 h, then filtered under argon. The filtrate is concentrated in vacuo and toluene is added to give a final volume of 50 mL. The concentration of reactive allylboronate is determined by treatment of a 1 mL aliquot of this solution with a known excess of cyclohexanecarboxaldehyde. This... 

To a —78 C solution of 23.1 mL (100 mmol) of triisopropyl borate and 8.15 mL (110 mmol) of 3-chloro-l-propene in 100 inL of dry THF is added dropwisc via a cannula over 0.5 h a solution of LDA (110 mmol prepared in 200 mL of THF from 110 mmol of diisopropylamine and 47.9 mL of 2.3 M butyllithium in hexane), This mixture is stirred for an additional 0.5 h at — 78 "C then a solution of 75.9 ntL of 2.9 M anhyd hydrogen chloride in diethyl ether is added and the mixture is allowed to warm to 25 °C. The mixture is concentrated in vacuo (20 Torr) and the residue extracted with three 100-mL portions of pentane, Filtration under nitrogen followed by distillation under reduced pressure provides 18.0 g (88%) of diisopropyl l-chloro-2-propenylboronate bp 95-96 "C/25 Torr. Transesterification of this intermediate with 1.3-propanediol provides the title compound in almost quantitative yield bp 110-112°C/20Torr. 

The synthesis of L-ribose required two significant innovations for its completion. The first was an efficient synthesis of diisopropyl (chloromethyl)boronate (1) via the in situ preparation of (chloromethyl)lithium by addition of butyllithium to a mixture of chloroiodomethane and triisopropyl borate in THF at — 78°C 18. 

An alternate synthesis is outlined in Scheme 2.1 2 Diisopropyl dichloromethylboronate (6) is readily prepared by reacting triisopropyl borate with dichloromethyllithium prepared in situ. 20 Transesterification with a suitable C2 symmetric diol gives an ester 7 that can be treated with an alkylmagnesium bromide to yield chloride 8 and then, after transesterification with pinanediol (see Section 15.1.7.2) a product 9 which is analogous to 3. 

Figure 1. XANES spectra for crystallographically characterized Mn(II), Mn(III), and Mn(IV) model compounds. Long dashed lines indicate Mn(II) compounds solid lines indicate Mn(III) compounds short dashed lines indicate Mn(IV) complexes. The models chosen to illustrate this phenomenon are[Mn(ll)HB(3,5-iPr2pz) 3]2(OH) 2and(pyrazolyl) 2Mn(OCfi3) 3Mn(ll) (HB 3,5-iPr2pz)3 [where HB(3,5-iPr2pz)3 is hydrotris(3,5-diisopropyl-1-pyrazolyl borate) Mn(II)(hexakisimidazole)Cl2 Mn(III)(acac)3 Mn(III)2, [2-OH-(5-Cl-SAL)PN]2(CH3OH), [Mn(IV) (n2-0) (SALPN)]2, and [Mn(IV)-(SALPN)]2(h2-0)(h2-OH) [where SALPN is l,3-bis(salicylideneimanato) propane] [Mn(III) (SALAHP) (AcO)]2 [where SALAHP is 3-(salicylideneim-inato)-2-methyl- 1,3-dihydroxy propane] and Mn(IV) (SALADHP) 2 [where SALADHP is the dianion of 2-methy 1-2-(salicylideneamino)-1,3-dihydroxy-propane].

TCNE = Tetracyanoethylene Dipdba = 4,4 -diisopropyl(di-benzylideneacetone) TMM = Trimethylenemethane dppm = (Diphenylphosphino)methane MMLCT = Metal-metal bond to ligand charge-transfer Tp = Hydrido(trispy-razolyl)borate Tp = Hydridotris(3,5-dimethyl-pyrazolyl)bo-rate BAr = (3,5-triflnoromethylphenyl)borate ttab = l,2,4,5-tetrakis(l-iV-7-azaindolyl)benzene tmeda = Tetra-methylethylenediamine bpma = Bis(pyridyhnethyl)amine TFE = Triflnoroethanol dtbpm = Bis(di-terr-butylphosphi-no)methane dmpe = Bis(dimethylphosphino)ethane dcpe = Bis(dicyclohexylphosphino)ethane triphos = Bis(2-diphe-nylphosphinoethyl)phenylphosphine COD = 1,5-cycloocta-diene dppbts = (Diphenylphosphinobutane)tosylate sodium PPE = Poly(jo-phenylene ethylene). 

Figure 16 Structural diagram and 647.1-mn excitation RR spectrum of the blue copper site analog complex, LCu(ll)-SR (L = hydrotris(3,5-diisopropyl-l-pyrazolyl)borate). A single Cu-S stretching mode is seen in the RR spectrum, as expected from excitation into RS —Cu CT transition of a chromophore containing only one terminal Cu-S bond...

Preparative Methods prepared by the reaction of Triisopropyl Borate and Allylmagnesium Bromide in Et20 followed by an acidic extractive workup and direct esterification with diisopropyl tartrate (DIPT) (eq 1). ... 

Dipicolinicacid,H20/1 -(2-pyridylazo-)-2-naphthol,pyridine/ Tris(3,5-diisopropyl-pyrazol-l-yl)borate, h2o 3,1 22 152-154... 

Triisopropyl borate (98.2 mL. 425 mmol) is slowly added to the flask via cannula, by controlling the internal temperature lower than -65 °C (ca 2 h). After stirring for 10 min at -78 °C, the reaction mixture is rapidly poured into a 2 L separatory funnel containing IN HCl (800 mL) saturated with NaCl. The aqueous layer is adjusted to pH 1 by addition of additional IN HCl. A solution of (R,R)- diisopropyl tartrate (100 g, 425 mmol) in ether (150 mL) is added. The aqueous layer is removed, and the aqueous... 

The hydrotris[(3,5-diisopropyl)pyrazolyl]borate derivative [Mn " (HB(3,5-iPr2pz)2(3-iPr0-5-iPrpz))]2(/t-0) (263) (Fig. 43), has a similar Mn-Mn distance, 3.53 A, and a more linear Mn-O-Mn geometry explained by steric demands of the hindered HB(3,5-iPr2pz)2(3-iPrO-5-iPrpz) ligand. The Mn complex with tetraphenyl porphyrin forms an oxo-bridged complex, [Mn (TPP)N3]2(jU.-0), with a nearly linear Mn-... 

Co = Catechol oxidase He = Hemocyanin Tyr = Tyrosinase MePy2 = Al,Al-bis(2-pyridylethyl)methylamine TACN = 1,3,5-triazocyclononane TMPA = Tris[(2-pyridyl) methyl]amine XYL-0 = a, a -bis[Al,Al-bis(2-pyridylethyl) amino]-m-xylene-2-olate XYL = a, a -bis[Al,Al-bis(2-pyri-dylethyl)amino]-m-xylene XYL-R = Meta substituted a,a bis[Al,Al-bis(2-pyridylethyl)amino]-m-xylene N3 = N, N, Al, Al -Tetrakis-(2-pyridin-2-yl-ethyl)-propane-1,2-diamine N4 = Al,Al,Al, Al -Tetrakis-(2-pyridin-2-yl-ethyl)-butane-1,2-diamine N5 = Al,A,lV, Al -Tetrakis-(2-pyridin-2-yl-ethyl)-pentane-1,2-diamine HB(3,5-Pr2pz)3 = Hydrotris(3, 5-diisopropyl-l-pyrazolyl) borate XAS = X-ray absorption spectroscopy EXAFS = Extended X-ray absorption fine structure rR = resonance Raman. 

TCNE = Tetracyanoethylene Dipdba = 4,4 -diisopropyl(di-benzylideneacetone) TMM = Trimethylenemethane dppm = (Diphenylphosphino) methane MMLCT = Metal-metal bond to ligand charge-transfer Tp = Hydrido(trispy-razolyl)borate Tp = Hydridotris(3,5-dimethyl-pyrazolyl)bo-rate BAr 4 = (3,5-trifluoromethylphenyl) borate ttab =... 

Steric constraints similar to those of triphos are apparently also exerted by the tm(pyrazolyl)borate ligands with 3,5 diisopropyl substituents and indeed the dicopper(II) complex (HBz)Cu(//-S2)Cu(HBz)], 15, is another known example of a S bridge in electron rich L6M2 unpuckered frameworks.The latter species... 

Fig. 16. Resonance Raman spectra (647.1 nm excitation) of the blue copper site analog complex, LCuCIIlSCHfCHslC Hs [L is hydrotris(3,5-diisopropyl-l-pyrazolyl) borate], with natural abundance iec-butyl thiolate (top) and the C -deuterated isotopomer (bottom). ...

Simple (halomediyl)boronic esters are not accessible by methods used for higher homologs. The discovery that (chloromethyl)lithium can be generated at -78 C from chloroiodomethane by treatment widi butyllithium in the presence of triisopropyl borate and captured immediately to form the (chloromethyl)borate salt and, after acidification, the boronic ester has provided practical access to these useful reagents [33]. The less expensive reagent dibromomethane under similar conditions generates (bromomethyl)lithium and yields (bromomethyl)(triisopropyl)borate anion (42), which is converted into diisopropyl (bromomethyl)boronate (43) by treatment with anhydrous hydrogen chloride or, more conveniently, methanesulfonic acid while the reaction mixture is still cold (Scheme 8.8) [34]. 

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