Borane in THF

Hvdrow-undecansaure 4,6 g (25 mMol) Undecen-(10)-siiure werden in 100 ml THF unter Stickstoff mit 50 mMol Bis-[3-methyl-butyl-(2)]-boran in THF versetzt. Es entwickeln sich 24 mMol Wasserstoff. Man riihrt 30 Min. und versetzt mit 20 ml 3 n Natriumlauge und 15,5 ml (170 mMol) SS Vnigem Wasserstoffperoxid. Das erhaltene Rohprodukt wird aus Wasser kristallisiert Ausbeute 4,13 g (R2°/o d. Th.) F 68-69". 

Mit Diboran bzw. Bis-[3-methyl-butyl-(2)]-boran in THF werden bei -5bis0°43-52bzw. 74% d. Th. Diphe-... 

XII), which is then reduced with borane in THF to produce (VI). The trimethoxy secondary amine (VI) is demethylated by refluxing its solution in glacial acetic acid and HBr to yield dobutamine hydrobromide... 

A solution of 7mM of the indolyglyoxamide in 160 ml tetrahydro-furan and 30 ml (30mM) l.OM borane in THF is refluxed 2 hours and cooled. Carefully add water, then evaporate in vacuum and dissolve residue in ether. Wash twice with saturated saline, dry and evaporate in vacuum. Triturate with ether and filter to get the tryptamine-borane in ca. 30% yield. Diss. 200 mg in 2 ml xylene and 2 ml octene-1 and reflux 4 hours. Cool, dilute with hexane and filter to get ca. 80 mg white tryptamine (or dialkyltryptamine) (recrystallize-acetone-hexane etc.). 

In the asymmetric reduction of ketones, stereodifferentiation has been explained in terms of the steric recognition of two substituents on the prochiral carbon by chirally modified reducing agents40. Enantiomeric excesses for the reduction of dialkyl ketones, therefore, are low because of the little differences in the bulkiness of the two alkyl groups40. In the reduction of ketoxime ethers, however, the prochiral carbon atom does not play a central role for the stereoselectivity, and dialkyl ketoxime ethers are reduced in the same enantiomeric excess as are aryl alkyl ketoxime ethers. Reduction of the oxime benzyl ethers of (E)- and (Z)-2-octanone with borane in THF and the chiral auxiliary (1 R,2S) 26 gave (S)- and (R)-2-aminooctane in 80 and 79% ee, respectively39. 

When aromatic nitro compounds are reduced with zinc and water under neutral conditions,51 5 hydroxylamines are formed. Among other reagents used for this purpose have been Sml ,v" N H4-Rh-C.,g7 and NaBH4-Se.5w Borane in THF reduces aliphatic nitro compounds (in the form of their salts) to hydroxylamines 5 1 ... 

N-(4-Nitrophenethyl)-l,2,3,4-tetrahydro-6,7-dimethoxy-l-methylisoquinoline N-(4-Nitrophenylacetyl)-l, 2,3,4-tetrahydro-6,7-dimethoxy-l-methylisoquinoline (62.9 g, 0.17 m) was added portion-wise to 500 ml of 1 M borane in THF which was diluted with 500 ml THF and maintained under nitrogen. The mixture was stirred at ambient temperature for 1 hr then heated to reflux for 4 hr. The mixture was then cooled in an ice bath and treated carefully with 20% HCI (250 ml). The mixture was refluxed for 1 hr, cooled and then the solvents evaporated on an aspirator. Water (1 liter) was added and the solution basified to pH 11 with 50% NaOH, then extracted with CHCI3 (3 x 300 ml). 

Arylboronic acids are readily available via transmetalation between ArSnMe3 and borane in THF. Consequently, a variety of arylpolyboronic acids is achievable from the stannanes previously synthesized by the SRN1 mechanism from ArCl or ArOH in around 80% yields [50, 51]. These arene di- and tri-boronic acids can be used as starting materials for the synthesis of polycyclic aromatic systems via double or triple Suzuki crosscoupling reactions [50, 51], as shown in Scheme 10.34 [51],... 

Aryltrimethyl stannanes are easily transformed into boronic acids by transmetalation with borane [106]. Thus, 1,4- and 1,3-Z>fy(trimethyl-stannanyl)benzenes as well as 2,5- and 2,6-Z /s(trimethylstannyl)pyridines synthesized by the SRN1 mechanism, react with borane in THF to give intermediates which on hydrolysis lead to benzene- and pyridinediboronic acids (Sch. 35) [107]. 

Reaction of a 5-alkoxy derivative with NaBD4 gave the 5,5-dideutero derivative exclusively <87JHC25l>. Reduction of the compounds (79) with borane in THF gave the amines (81), whose oxidation with DDQ in AcOH afforded the derivatives (80) <92JMC320>. 

To avoid isolating the glycal, the reaction was quenched with an excess of borane in THF and, upon oxidative work-up under basic conditions, C-disaccharide 38 was obtained in 64% yield over two steps (Scheme 11) (77). The stereochemistry of the hydroboration step was verified on the corresponding acetate by examination of the Jy%T and J2 y coupling constants in the proton NMR spectra. 

An inexperienced graduate student treated dec-5-ene with borane in THF, placed the flask in a refrigerator, and left for a... 

If a C3 unit needs to be introduced bearing a carbon chain, then there are several options. A P-amino add could be used as a precursor in a parallel synthesis to those discussed above. Alternatively, a strategy based on malonate syntheses could be employed. Co-condensation of a C-substituted malonate with a primary diamine in boiling ethanol gives reasonable yields of cyclic diamide which may be reduced with borane in THF to yield the desired polyamine (Scheme 1.12 and Protocol 5).18 Another possibility is to prepare a linear bis-toluenesulfonate ester from a malonate by reduction (e.g. LiBH4) and tosylation, followed by a standard toluenesulfonamide cyclisation reaction. Yet another variant, this time giving racemic product, is to react a coumarin derivative with a linear polyamine (Scheme 1.12).1819 In this case, a... 

Hydration with boranes proved difficult due to extensive reductive cleavage of the epoxide (Scheme 45). The best results (54%) were achieved with borane in THF. The subsequent oxidation with basic hydrogen peroxide led to the primary alcohol as well as to saponification of the acetate. Selective protection of the primary alcohol 397 as trichloroethyl carbonate was followed by oxidation with RuCl3/NaI04, thereby producing not only the y-lactone but also the cyclic ketone. 

This reaction is general , with simple routes to trialkylhydroborates available. The method is effective for boranes from B(C2Hj)3 to such complex ones as phenyl-9-borabicyclo[3.3.1]nonane . Reaction occurs when a slight xs of (t-C4H,)Li in pentane is added dropwise to borane in THF at — 78°C with vigorous stirring. The lithium trialkylhydroborate is formed quantitatively ... 

We have found that chemical modification of the olefins with any of a variety of borane reagents followed by oxidation allows for their quantitative removal from shale oils by elution chromatography on deactivated alumina. The method is so thorough that aromatic olefins such as indene are removed completely. The reagents which have been used successfully are borane in THF, borane-methylsulfide complex (RMS), and 9-borabicyclo [3.3.1.]nonane-(9-BBN), all of which are commercially available. The use of borane in THF has been discontinued in our laboratory because BMS gives the same result, is more stable, and is easier to handle. 

Reduction of the free carboxylic acid in an otherwise fully protected uronic acid can be accomplished with borane in THF [ 169]. For example, the borane-THF complex reduces diisopropy-... 

The reagent (1) is prepared in 80% yield by the reaction of catechol with borane in THF.1 The borole reacts with olefins at 100° to give the corresponding 2-alkyl--... 

Yields are in the range 77-98% with organoboranes derived from 1-alkenes yields are lower with sterically hindered trialkylboranes. The hydrolytic step is conveniently accomplished by addition of water to the solution of the organo-borane in THF prior to addition of diazoacetaldehyde.1... 

In this process (Fig. 22), ketone 61 underwent reduction with an over-stoichiometric amount of borane in THF in the presence of 5 mol % of the proline-derived Corey s oxa-zaborolidine 62 to afford alcohol 63 in 100% yield and 92% e.e. SN2 displacement carried out on the alcohol mesylate with a higher-order cuprate gave adduct 64, that was transformed first into tetralone 65 by a triflic acid-promoted Friedel-Crafts-type reaction, and then into sertraline 66 (86% e.e.) by imine formation and borohydride reduction. 

One-carbon homologation of organoboranes. The reaction of trialkyl-boranes in THF with this a-lithio derivative of dimethyl sulfide in TMEDA results in formation of an a-thioorganoborate anion, detectable by NMR. Addition of methyl iodide (or methyl fluorosulfonate) results in homologation. 

A complimentary approach to asymmetric catalytic reduction is based on bo-rane mediated hydride transfer. ACTCs 14 to 18 when treated with a solution of borane in THF are assumed to form catalysts of a structure such as D [20]. 

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