Borane reaction with boron trichloride

Tris(dimethylamino)borane has been prepared by dimethyl-aminolysis of boron trichloride, with or without solvent,1-5 and by the reaction of boron trifluoride with dimethylamine in the presence of a suitable Grignard reagent.6 The procedure described here is a modification of the reaction of dimethylamine with boron trichloride in pentane as the solvent. 

Bidentate boranes with an o-phenylene backbone constitute some of the simplest examples of polydentate Lewis acids with rigid backbones. They can be prepared by the reaction of boron halides with a 1,2-dimetallated benzene derivative. Thus, the reaction of 1,2-bis(chloromercurio)benzene (5) with boron trichloride affords 1,2-bis(dichloroboryl)benzene (6, Scheme 3). ... 

Weber and coworkers reported the synthesis of novel substituted borazoles. The reaction of boron trichloride with 1,2-diimines 367 provide a mixture of products. The formation of dimeric borazole 369 was explained based on a nucleophilic attack of the chloroborane 370 on the ate complex 368 followed by dehydrohalogenation. Alternatively, a controlled addition of BCR to the diimine 367 results in a clean formation of the imine-borane complex 373 that upon reduction with sodium amalgam and calcium hydride provided the chloroborazole 375 (Scheme 59) <2006EJI5048>. 

It is most conveniently stored in glass ampuls. Several other preparations for this compound are known including reactions of dihydroxy(phenyl)borane and boron trichloride12 13 or phosphorus pentachloride,14 2,4,6-triphenylboroxin, [C6H5BO]3, with phosphorus pentachloride,14 phenyl mercury chloride with boron trichloride,15 and benzene with boron trichloride.16... 

For instance, attempts at isolating donor-free alkynylboranes have been hampered by spontaneous polymerization. The first donor-free tris(alkynyl)borane, tris(3,3-dimethyl-l-butynyl)borane (30), has only recently been obtained by reaction of deprotonated 3,3-dimethyl-l-butyne with boron trichloride at —78°C in pentane (equation 32). The alkynylborane (30) was fully characterized by multinuclear NMR spectroscopy, mass spectrometry, and X-ray crystallography. The NMR signal of (30) shows a remarkable shift of 5 = 48, which is upfield from typical shifts of alkyl-and alkenylboranes. The crystal structure of (30) shows similar C-C bond lengths, but significantly shorter B-C bonds in comparison to those observed for the donor-stabilized complexes (30) D indicative of a small degree of p - p interactions between the sp -boron atom and the sp-hybridized carbon. Weak r-overlap was further confirmed by ab initio calculations. It is this r-interaction that has been exploited for the development of nonlinear optical (NLO) materials based on alkynylboranes as described in Section 7.1. ... 

Direct boronation of benzene derivatives with BCI3 in the presence of activated aluminum or AICI3 provides arylboronic acids after hydrolysis (eq 12). Chloroboration of acetylene with boron trichloride produces dichloro(2-chloroethenyl)borane. Similar reaction with phenylacetylene provides ( )-2-ehlorO 2-phenylethenylborane regio- and stereoselectively. ... 

Boron trichloride undergoes several exchange reactions with dihorane, other boron halides and trialkyl-, triaryl-, or triaryloxy boranes (Lower, L.D. 1978. Boron compounds (halides). In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd. ed. pp 129-135. New York Wiley Interscience). The reactions occur at ambient or lower temperatures ... 

Tris(N-methylanilino)borane has previously been prepared by the reaction of boron trifluoride-ether complexes with three equivalents each of N-methylaniline and a suitable Grignard reagent,1,2 by the reaction of (N-methylanilino)potassium with boron trifluoride-ether complexes,2 and by aminolysis of boron trichloride by N-methylaniline.3 The present general procedure describes a convenient preparation of tris(N-methylanilino)-borane by the reaction of (N-methylanilino)lithium and boron trifluoride-diethyl ether in tetrahydrofuran-hexane as solvent. 

Preparation. The reagent is prepared by the reaction of borane (516 mmole) in THF with a freshly prepared solution of boron trichloride (1032mmole 1, 67-68 2, 34-35 3, 31-32) in THF at 0°. The reagent is stable for several months at 0°. 

Dichloroborane and monochloroborane etherates or their methyl sulfide complexes have been prepared by the reaction of borane and boron trichloride [44]. The hydroboration of alkenes with these borane reagents is, however, usually very slow because of the slow dissociation of the complex. Dichloroborane prepared in pentane from BCI3 and trimethylsilane is unusually highly reactive with alkenes and alkynes hydroboration is instantaneous at -78 °C (Eq. 20) [45]. 

Bayer and Siebert reported the reaction of 3,3-dimethyl-l-butyne with -BuLi in pentane, followed by the addition of boron trichloride to afford the intermediate dichloro(3,3-dimethylbut-l-ynyl)borane that was hydroborated with dichloroborane formed in situ to give l,l-bis(dichloroboryl)-3,3-dimethylbutene 51 (Scheme 6) <2002ZN1125>. When the latter was subjected to halogen exchange with boron triiodide, it was converted into the corresponding tetraiodide 52, which underwent a redox reaction with hex-3-yne to give the 2-(2,2-dimethylpropylidene)-l,3-diborole 22 in 73% yield. 

Chloroboranes are another class of heteroatom-substituted boranes. Dichloroborane (CI2BH) and mono-chloroborane (CIBH2) are formed by the reaction of diborane with varying proportions of boron trichloride etherate (BCl3 OEt2). In ether solvents, both reagents are formed as the etherate.23 An alternative synthesis was the reaction of HCl with borane THF,24 but reduction of boron trichloride with lithium borohydride in ether proved to be the most useful route.23... 

Arylboronic and arylborinic acids have been produced from the hydrolysis of intermediates in the reactions of aryl-tin and aryl-lead compounds with diborane. The preparation of di[bis(trimethylsilyl)methyl]chloroborane from the reaction of bis(trimethylsilyl)methyl-lithium and boron trichloride has been published. A new reagent for O-ethylboranediylation, ethylbis-(2-isopropyl-6-methyl-4-pyrimidinyloxy)borane (3) has been synthesized and used to prepare O-ethyl-boranediyl derivatives of alcohols, phenols, alkanediols, D-mannitol, and l-arabinose. Borane-methyl sulphide reportedly reacts smoothly with primary, secondary, and tertiary alcohols and phenols to provide a general and convenient synthesis of borate esters. ... 

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