Boranes trialkoxy

Borane, 1-methylbenzylaminocyanohydropyrrolyl-, 3, 84 Borane, thiocyanato-halogenohydro-, 3,88 Borane, trialkoxy-amine complexes, 3, 88 Borane, triaryl-guanidine complexes, 2,283 Borane, trifluoro-complexes Lewis acids, 3,87 van der Waals complexes, 3, 84 Borane complexes aminecarboxy-, 3,84 aminehalogeno-, 3, 84 amines, 3, 82, 101 B-N bond polarity, 3, 82 preparation, 3, 83 reactions, 3, 83 bonds B-N, 3, 88 B-O, 3, 88 B-S, 3, 88 Jt bonds, 3, 82 carbon monoxide, 3, 84 chiral boron, 3, 84 dimethyl sulfide, 3, 84 enthalpy of dissociation, 3, 82... 

Most reported boric acid esters are trialkoxy or triaryloxy boranes. The esters range from colorless low boiling Hquids to soHds that possess high melting points. Boric acid esters usually have an odor similar to the hydroxy compound from which they are derived. A more complete description of the physical... 

The triaLkoxy(aryloxy)boranes are typically monomeric, soluble in most organic solvents, and dissolve in water with hydrolysis to form boric acid and the corresponding alcohol and phenol. Although the rate of hydrolysis is usually very fast, it is dependent on the bulk of the alkyl or aryl substituent groups bonded to the boron atom. Secondary and tertiary alkyl esters are generally more stable than the primary alkyl esters. The boron atom in these compounds is in a trigonal coplanar state with bond hybridization. A vacantp orbital exists along the threefold axis perpendicular to the BO plane. 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

Diboran reduziert Monocarbonsauren in THF oder 1,2-Dimethoxy-athan, mit dem Losungsmittel als Boran koordiniert, in zwei Schritten. Zuerst wird bei -20° schnell und quantitativ Triacyloxy-boran gebildet, im zweiten langsameren Schritt (25°, 1 Stde.) Trialkoxy-boroxol, das nach Hydrolyse den gewiinschten Alkohol liefert4. 

Ebelman and Bouquet prepared the first examples of boric acid esters in 1846 from boron trichloride and alcohols. Literature reviews of this subject are available. B The general class of boric acid esters includes the more common orthoboric acid based trialkoxy- and triaryloxyboranes, B(0R)3 (1), and also the cyclic boroxins, (ROBO)3, which are based on metaboric acid (2). The boranes can be simple trialkoxyboranes, cyclic diol derivatives, or more complex trigonal and tetrahedral derivatives of polyhydric alcohols. Nomenclature is confusing in boric acid ester chemistry. Many trialkoxy- and triaryloxyboranes such as methyl, ethyl, and phenyl are commonly referred to simply as methyl, ethyl, and phenyl borates. The lUPAC boron nomenclature committee has recommended the use of trialkoxy- and triaryloxyboranes for these compounds, but they are referred to in the literature as boric acid esters, trialkoxy and triaryloxy borates, trialkyl and triaryl borates or orthoborates, and boron alkoxides and aryloxides. The lUPAC nomenclature will be used in this review except for relatively common compounds such as methyl borate. Boroxins are also referred to as metaborates and more commonly as boroxines. Boroxin is preferred by the lUPAC nomenclature committee and will be used in this review. 

Another convement method, for the preparation of higherboiling trialkoxy- and triaryloxyboranes, in particular, is the transesterification of lower-boiling boranes (equation 10). The lower boiling alcohol is removed continuously by distillation. 

Aluminum sesquihalides " or even mixtures of metallic Al, alkyl halide and trialkoxy-borane, can also be used. Trialkoxyboroxines, from trialkoxyboranes and boron trioxide, are convenient boron substrates ... 

Since the boroxines are readily available from B203 and trialkyl boranes or trialkoxy boranes, they are in effect reactions of boron oxide with trialkyl alanes. Gallium tribromide and triethylalane give triethylgallane in over 80% yield, but only the first alkyl group on aluminum is involved in alkylation (63, 65) ... 

The conversion of boron compounds to trialkoxy boranes is the basis for a widely used historic prospecting procedure for identification of borate minerals. By adding a mineral acid and methanol to a ground mineral sample and then igniting the mixture, one can observe whether it burns with the green flame of volatile methyl borate. 

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