Borane tetrahydrofuran complex

A more convenient hydroboratmg agent is the borane-tetrahydrofuran complex (H3B THF) It IS very reactive adding to alkenes within minutes at 0°C and is used m tetrahydrofuran as the solvent... 

Examine the electrostatic potential map of H3B THE (borane-tetrahydrofuran complex) on Learning By Modeling How does the electrostatic potential of the hydrogens bonded to boron dif fer from the potential of the hydrogens of the tetrahydrofuran ring" ... 

Scheme 4 outlines the synthesis of key intermediate 7 in its correct absolute stereochemical form from readily available (S)-(-)-malic acid (15). Simultaneous protection of the contiguous carboxyl and secondary hydroxyl groups in the form of an acetonide proceeds smoothly with 2,2 -dimethoxypropane and para-toluene-sulfonic acid and provides intermediate 26 as a crystalline solid in 75-85 % yield. Chemoselective reduction of the terminal carboxyl group in 26 with borane-tetrahydrofuran complex (B H3 THF) affords a primary hydroxyl group that attacks the proximal carbonyl group, upon acidification, to give a hydroxybutyrolactone. Treat-... 

Borane-tetrahydrofuran complex Furan, tetrahydro, compd. with borane (1 1) (8,9) (14044-65-6)... 

Hydroboration-oxidation is a useful method when the desired product is the anti-Mcirkovnikov alcohol. The borane-containing reactant is normally dibo-rane (B2Hg) or the borane tetrahydrofuran complex (BHj THF). No matter what hydroboration agent is used, it s usually simplified to BH3 in the mechanism. BH3 is a useful reactant because it s a good Lewis acid. 

Introduction of the C2 sulfonamide is accomplished via sulfonylation with chlorosulfonic acid, conversion to the sulfonyl chloride using thionyl chloride, and amidation using concentrated ammonium hydroxide in tetrahydrofuran. Reduction of the 4-acetamido compound using borane-tetrahydrofuran complex provides the 4-ethylamino derivative. The 45,65-frans diastereomer is selectively crystallized as its maleate salt from acetone in the presence of the unwanted 4R,6S-cis diastereomer. Neutralization of the maleate salt and extraction of the free base in ethyl acetate, followed by formation of the hydrochloride salt, yields crude dorzolamide hydrochloride. 

A 0.5 M solution of 9-BBN in tetrahydrofuran was purchased from Aldrich Chemical Company, Inc., and was used without additional purification. The preparation2 of the reagent by hydroboration of 1,5-cyclooctadiene with borane/tetrahydrofuran complex is reported. 

Compound with 9S-cinchonan-9-ol (3974950-3), 67, 1 Borane-dimethylsulfide (13292-87-0), 68, 77 Borane, tetrahydrofuran complex, 69, 214... 

Acetyl chloride Acetic acid potassium Borane-tetrahydrofuran complex 2,2-Dimethoxypropane Sodium hydroxide... 

Methyl 2-(2-iodophenyl)propanoate Tetrabutylammonium chloride Diethyl 1,1-cyclopropanedicarboxylate Vinyl magnesium bromide Methyl magnesium chloride Borane-tetrahydrofuran complex Diisopropylethylamine Methanesulfonyl chloride... 

Borane-tetrahydrofuran complex (1.0 M) was obtained from Aldrich Chemical Company, Inc., and the concentration of the solution determined using the literature procedure.3... 

Treatment of cyanoethylcellulose with borane-dimethylsulfide or borane-tetrahydrofuran complexes in tetrahydrofuran has resulted in the quantitative conversion to 3-aminopropylceIlulose. Such aminopropylcellulose derivatives have also been employed as intermediates for acetamido or aryluredo products, and in grafting reactions [119]. 

Tetramethylethylenediamine, THE, sec-butyllithium, chlorodimethyloctylsilane THE, borane-tetrahydrofuran complex, hydrochloric acid CH2C12, vinyl chloroformate THE, potassium t-butoxide... 

The Step 2 product (2.3 mmol) dissolved in 30 ml of THE was treated with a borane-tetrahydrofuran complex (23 mmol) and then refluxed for 18 hours and quenched with water. The mixture was concentrated and treated with 6M hydrochloric acid and... 

Although the reagent is often the borane-tetrahydrofuran complex (BHjiTHF), other more highly substituted, more stcrically demanding, alkylboranes (RBH and R,BH) are also used to enhance the stereoselectivity of the reaction. 

The rapid reaction between carboxylic acids and borane is related to the electrophilicity of the latter. The carbonyl group of the initially formed acyloxyborane intermediate, which is essentially a mixed anhydride, is activated by the Lewis acidity of the trivalent boron atom. Addition of 1/3 equiv of the Borane-Tetrahydrofuran complex to acrylic acid in dichloromethane followed by addition of a diene at low temperature results in the formation of Diels-Alder adducts in good yield (eq 1). Further, the reaction is successful even with a catalytic amount of borane. 

When fresh lithium aluminum hydride was used instead of the borane-tetrahydrofuran complex,3 the reduction gave low yields and the product was more difficult to purify. 

Borabicyclo[3.3.1]nonane (9-BBN) has been prepared by the thermal redistribution of 9-n-propyl-9-BBN, and the hydroboration of 1,5-cyclooctadlene with borane-tetrahydrofuran complex followed by thermal isomerization of the mixture of dialkylboranes at BS C. Solutions of 9-BBN have been prepared from the hydroboration of 1,5-cyclooctad ene with borane-methyl sulfide in solvents other than THF.6 The present procedure involves the cyclic hydroboration of 1,5-cyclooctadiene with borane-methyl sulfide in 1,2-dimethoxyethane.7 Distillative removal of the dimethyl sulfide in this special solvent system provides a medium that gives high purity, large needles of crystalline 9-BBN dimer in excellent yield. The material can be handled in air for brief periods without measurable decomposition. 

Aminoethoxy)ethanol, acetic anhydride (99+%), thionyl chloride (99+%), benzylamine (99%), 1,2-bis(2-iodoethoxy)ethane (98%), anhydrous sodium iodide (99+%) and borane-tetrahydrofuran complex (1.0 M solution in tetrahydrofuran) were purchased from Aldrich Chemical Company, Inc. and were used without further purification. 

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