N-Butylborane

Although dimeric (t-butylmethyleneamino)dibutylborane can be prepared by the reaction of tri-t-butylborane with pivalonitrile at temperature above 150 °C by elimination of butene. preparation at lower temperatures involving triethylamine-borane according to Eq. (11), illustrates that the formation of this iminoborane proceeds via di-n-butylborane as an intermediate 6 ... 

B-halogenated iminoboranes were also obtained by treating (t-butylmethyl-eneamino)di-n-butylborane (c.f. (Ill) with trihaloboranes at elevated temperatures 4 6 >. 

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. 

Methylthiomethylesters.1 Treatment of DMSO with n-butyllithium followed by tri-n-butylborane affords the ate complex CH3S(0)CH2BBu3Li+(l), which converts acid chlorides into methylthiomethyl esters. 

The triplet ketones, R2C—6, are a special case of alkoxyl radicals. Thus UV irradiation of acetone and tri-n-butylborane in the cavity of an ESR spectrometer led to the observation of two radicals, CMejOBBu", Eq. (21), and Bu". On a preparative scale the coupled products as well as BunMe2COBBu2 were isolated. 

It was early reported that perbenzoic acid in chloroform at room temperature quantitatively oxidizes tii-n-butylborane as in equation (37), The reaction with peroxytrifluoroacetic acid has been used analytically but very little in synthesis. 

Brown ei al. now find that tri-/i-butylcarbinol is obtained in essentially quantitative yield by the reaction of tri-n-butylborane with chlorodifluoromethane (or other tri-substituted methanes) under the influence of lithium triethylcarboxide (equation 2). 

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. 

Triazine, 410 Tri-n-butylborane, 410 Tri-n-butylcrotyltin, 411 Tri-n-butylcyanotin, 411 Tri-n-butylphosphine, 56 Tri-n-butyltin hydride, 307,411-413 Tri-n-butyltinlithium, 413-414... 

Preparation. A mixture of tri-n-butylborane and anhydrous boric oxide is refluxed under nitrogen for 40 hrs. and the product distilled. Under the same conditions tri-3ec-butylborane reacted with rearrangement to give tri-n-butylboroxine. 

It has been suggested that trialkylborane initiators form a complex with the radical end95. This has been shown by comparing the activation parameters for the tri-n-butylborane-initiated polymerization of vinyl trimethylacetate and of vinyl tri-fluoroacetate in various solvents with those for the AIBN-initiated polymerization (Table 2). The difference of stereoregulating activation parameters between the initiators may be due to the solvent effect on the formation of a complex of trialkylborane with the radical end. 

Tri-n-butylborane gives an 85 15 mixture of B-(n-butyl)borolane and B-(s-butyl)-borolane in 90% yield along with butenes and H2 ... 

These polymers have also been prepared by irradiation with a low-pressure mercury lamp and with a tri-n-butylborane-air initiation system [94]. 

A soln. of tri-n-butylborane in toluene added dropwise under Ng to a gently refluxing suspension of bis-(l,3-diphenyl-2-imidazolidinylidene) in toluene, and the product isolated after a few hrs. l,3-diphenyl-2-tri-n-butylmethyl-2-boraimidazolidine. Y 95%. F. e. s. G. Hesse and A. Haag, Tetrah. Let, 1965, 1123. 

A mixture of 1 mole phenyl isocyanide and 2 moles p-chlorobenzaldehyde in ether or tetrahydrofuran added dropwise to 1 mole tri-n-butylborane -> 2,2-di-n-butyl-4,5-di-p-chlorophenyl-3-phenyloxazolidine. Y 72%. G. Hesse, H. Witte, and W. Gulden, Ang. Gh. 77, 591 (1965). 

Different products are formed in diethyl ether and in THE, with an increased efficiency under sonication. The reaction applied to n-butyl bromide in ether gives tri-n-butylborane quantitatively, but the use of THF under identical conditions leads to an ate complex. The reactivity of the halides follows the normal sequence I > Br > Cl. Iodides give side reactions, making the use of bromides necessary. The metal of choice is magnesium, since lithium gives Wurtz-type products only. 

All trialkylboranes are readily oxidized in air. The lower members up to tri-n-butylborane are spontaneously inflammable, burning with the characteristic green boron flame. Peroxo intermediates are involved in the oxidations. Arylboranes are rather less sensitive to oxygen. 

Tri-n-butylborane allowed to react with formic acid at 150° tri-n-butyl-boroxine. Y 96%. M. Kumada, M. Ishikawa, and K. Yoshida, Mem. Fac. Eng., Osaka City Univ. 3, 201 (1962) G. A. 57, 2238e. 

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). 

---