6«-3-Methyl-2-butylborane

Compound (XIII) exists as a mixture of monomeric and dimeric species at room temperature. The same situation is true for the reaction products from methyl- and isopropyl-thiocyanate, respectively, with triisopropylborane, whereas the iminoborane obtained from reacting methyl-thiocyanate with tri-n-butylborane is dimeric 3 . With the exception of (XIII) these compounds have not been characterized by analysis. 

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... 

A graft copolymer of collagen (as well as other proteinaceous materials) with methyl methacrylate has been made by polymerization initiated by tri-n-butylborane (31). Kudaba and co-workers also modified collagen by treating it with epichlorohydrin (32, 33) or epoxy resins (34) with BFs Et20 as catalyst. Such treatments could be valuable for improving certain properties of leather, but the experimental conditions preclude their use for clinical applications. 

Apparent grafting to dentin and other proteinaceous materials has been reported through polymerization of methyl methacrylate with tri-n-butylborane (31, 54, 55, 56, 57). The mechanism on the top of p. 186 has been suggested. 

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%,... 

Hydroboration Anisole (solvent). Bls-3-methyl-2-butylborane. Diborane. 2,3-Dimethyl-2-butylborane. Triisopinocamphenyldiborane. 

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... 

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. 

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... 

C6H5-C = CHC4Hg-n from a-diazoketones. Ethereal methyllithium added dropwise at 0 to a soln. of di-n-butyl-(l-phenyl-l-hexenyloxy)borane prepared from diazoacetophenone and tri-n-butylborane in tetrahydrofuran, the ice bath removed, stirred 1 hr. at room temp., methyl iodide added, and stirring continued 1.5 hrs. 2-hexyl phenyl ketone. Y 69%. Via vinyloxyboranes, a,a- and ,/5-dialkylated ketones can be obtained in good yield from a-diazoketones and methyl vinyl ketone respectively. F. e. s. D. J. Pasto and P. W. Wojtkowski, J. Org. Chem. 36, 1790 (1971). 

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... 

Dimelhyl-2-butene added at 0° to 3.1 M borane in tetrahydrofuran to form thexylborane (2,3-dimethyl-2-butylborane), stirring continued 1 hr. at 0°, a soln. of isobutylene in tetrahydrofuran added and allowed to react 0.5 hr. at 0°, then ethyl vinylacetate added, allowed to stand 2 hrs. at 0°, water added, kept 3 hrs. at 50° under 70 atm. GO in a stainless-steel autoclave, transferred to a glass flask, 3 M Na-acetate added followed by O -HgOg at a rate to maintain the temp, at 30-40°, and kept 1 hr. at 50° — ethyl 7-methyl-5-oxooctanoate. Y 84%. - Because of the low migration aptitude of the thexyl group, either the same or two different olefins with a wide variety of functional groups can... 

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