Bis-3-methyl-2-butylborane

Use of selected alkylboranes for H—B addition to olefins has broadened the scope of hydroboration. Bis-3-methyl-2-butylborane (BMB), obtained as noted above as in (1) even in the presence of excess olefin, reacts with unsymmetrical olefins to give increased yields of the less hindered products and permits selective reactions not otherwise possible. Since, unlike diborune, it does not reduce carbonyl groups, the reagent can be used for hydroboration of an unprotected acid (2). r-Lactones react with only one mole of reagent, even when the latter is in excess (3). 

Use of a co-amine is embodied in an improved procedure for the preparation of A -octalin. A mixture of 0.2 mole of naphthalene and 250 ml. each of ethylamine and dimethylamine is placed in a flask fitted with a dry ice condenser, 1.65 g.-atoms of lithium wire cut in half-centimeter pieces is added all at once, and the mixture is stirred magnetically for 14 hrs. The solvent mixture is allowed to evaporate and the grayish white residue (containing excess lithium) is decomposed by cautious addition of about 100 ml. of water with cooling. The precipitated product is collected and the filtrate extracted with ether distillation affords 19-20 g. of hydrocarbon found by VPC analysis to contEiin 80% of A "-octalin and 20% of A -octalin. Isolation of the major product in pure form is accomplished by reaction of the mixture with bis-3-methyl-2-butylborane, which adds selectively to the less hindered A -isomer. Oxidation of the product with hydrogen peroxide to convert the adduct into an easily separated alcohol, followed by distillation, affords A" " -octalin of 99% purity in yield from naphthalene of 50-54%,... 

Bis-3-methyl-2-butylborane ( Disiamyl-borane ), 29, 31, 242 Bis-(p-nitrophenyl)hydrogen phosphate, 29-30... 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

The net effect is the conversion of terminal olefins into primary iodides by anti-Markownikoff hydroiodination. Note that only two alkyl groups react and the maximum yield isthus 66.7%. Yields actually obtained are close to this maximum. This difficulty can be circumvented by use of bis-3-methyl-2-butylborane (disi-amylborane, 1,57-59 2,29) rather than diborane ... 

Bis(ethylenediamine)chromium(II), 58 cfc-l,3-Bishydroxymethylcyclopent-4-ene, 172 1,3-Bis(hydr oxy phenyl) propane, 331 Bis-3-methyl-2-butylborane (Disiamylborane), 22-23, 27,160,187... 

Bisdithiocarbonates, 497 Bis(ethylthiolead), 522 Bishomoallylic alcohols, 62 Bismethoxycarbonylcarbene, 159 Bismethoxycarbonylcyclopropanes, 159 Bis-3-methyl-2-butylborane, 41 Bis(o-nitrophenyl) diselenide, 359 Bis(2,4-pentanedionato)nickel, 42 o, a-Bisphenylthiocyclohcptanone, 210 Bis(phenylthio)methane, 126... 

Undecenoic acid treated at 0° with a soln. of bis-3-methyl-2-butylborane in tetrahydrofuran, after 30 min. oxidized with alkaline HgOg -> ... 

The sterically hindered bis-3-methyl-2-butylborane, which is readily prepared in situ, exhibits a high selectivity for the less hindered of the two G-atoms of... 

It is clear from these representative results that regioselectivity in hydroboration is controlled by steric effects. As a result, nonsymmetric internal olefins usually yield a mixture of regioisomeric alkylboranes when they react with borane. Several hindered mono- and diakylboranes with sterically demanding alkyl groups, however, have been developed for use in selective hydroboration. Disiamylborane [bis(3-methyl-2-butyl)borane, 34], thexylborane (2,3-dimethyl-2-butylborane, 35), and 9-BBN (9-borabicyclo[3.3.1]nonane) are the most frequently used reagents. Improvements of regioselectivities in hydroboration of both... 

ALKENES Allyl dimethyldithiocarbamate. Bis(t -cyclopentadienyl)niobium trihydride. Cyanogen bromide. Di-n-butylcopperlithium. a,o-Dichloromethyl methyl ether. 2,3-Dimethyl-2-butylborane. N,N-Dimethyl dichlorophosphoramide. Diphenyl diselenide. Di-n-propylcopperlithium. Ferric chloride. Grignard reagents. Iodine. Lithium phenylethynolate. Lithium 2,2,6,6-tetramethylpiperidide. Methyl iodide. o-Nitro-phenyl selenocyanate. Propargyl bromide. rra s-l-Propenyllithium. Selenium. Tetrakis(triphenylphosphine)palladium. Titanium(IH) chloride. Titanium trichloride-Lithium aluminum hydride. p-Toluenesulfonylhydrazine. Triphenylphosphine. Vinyl-copper reagents. Vinyllithium. Zinc. 

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