Monochloroborane-dimethyl sulfide

Monohalogenoboranes are conveniendy prepared from borane—dimethyl sulfide and boron trihahdes (BX where X = Cl, Br, I) by redistribution reaction, eg, for monochloroborane—dimethyl sulfide [63348-81-2] (9) (81—83). Other methods are also known (84—87). 

Chlorothexylborane (1). Mol. wt. 132.44. One synthesis involves the reaction of thexylborane with 1 equivalent of hydrogen chloride in ether.1 This reagent can also be prepared by reaction of 2,3-dimethyl-2-butene with monochloroborane -dimethyl sulfide (equation I).2... 

Monochloroborane-dimethyl sulfide is an effective reagent for the chemo- and regiose-lective opening of oxiranes and cleavage of ethers (equation 180)1111. 

Thexylchloroborane-Dimethyl sulHde (1). This boranc can be prepared by treating thexylborane-dimethyl sulfide with hydrogen chloride or by hydroboration of 2,3-di-methyl-2-butene with monochloroborane-dimethyl sulfide. 

Molybdenum(V) chloride-Zinc, 274 Monochloroborane-dimethyl sulfide, 95 MontmoriUonite clay, 184 Morphoiinonaphthoquinones, 329-330 Muconic acid, 137, 138 Muscarine, 357 Muscarines, 18, 181, 182 Muscone, 35, 150... 

Methyl vinyl ketone, 177 Michael reactions, 129 Mimosamycin, 115, 116 Molecular sieves, 416, 486 Monochloroborane-Dimethyl sulfide, 354 Montmorillonite clay K-10, 507-508 Morphine, 102, 531 Morpholine, 459,486... 

Preparative Methods most conveniently prepared from commercially available monochloroborane-dimethyl sulfide complex and 2,3-dimethyl-2-butene in CH2CI2 (eq 1). ... 

The products are Hquids, soluble in various solvents and stable over prolonged periods. Monochloroborane is an equiUbtium mixture containing small amounts of borane and dichloroborane complexes with dimethyl sulfide (81). Monobromoborane—dimethyl sulfide complex shows high purity (82,83). Solutions of monochloroborane in tetrahydrofuran and diethyl ether can also be prepared. Strong complexation renders hydroboration with monochloroborane in tetrahydrofuran sluggish and inconvenient. Monochloroborane solutions in less complexing diethyl ether, an equiUbtium with small amounts of borane and dichloroborane, show excellent reactivity (88,89). Monochloroborane—diethyl etherate [36594-41-9] (10) may be represented as H2BCI O... 

RCH=CHZ —> RCHJCHODialkylchloroboranes, obtained as the major products of hydroboration of 1-alkenes with monochloroborane complexed with dimethyl sulfide, are oxidized by PCC to aldehydes (66-68% yield). Similar oxidation of dialkylchloroboranes derived from cyclic alkenes with PCC gives ketones in 70-85% yield. 

The preparation of monochloroborane in ether is capricious and the product is not stable. A more convenient source of monochloroborane is its dimethyl sulfide complex, which is readily prepared by reaction of borane-dimethyl sulfide with either tetrachloromethane (equation 22) or trichloroborane-dimethyl sulfide (equation 23). The latter reaction has also been modified for synthesis of the bromoborane and iodoborane complexes. 

If alkyldichloroboranes are specifically required, dichloroborane-dimethyl sulfide is the reagent of choice. It is more stable and more convenient than the dichloroborane-diethyl ether complex, but its hydroborating properties are very similar." Dichloroborane complexes ethers even more strongly than monochloroborane, and its reactions with alkenes in this solvent are slow and lead to mixtures. Therefore, it is generally used in pentane and trichloroborane is added to liberate uncomplexed dichloroborane. Under these conditions it readily gives alkyldichloroboranes on reaction with alkenes or alkenyldichloro-boranes on reaction with alkynes. " " The latter reaction has been applied to alkynylsilanes (equation 44)." ... 

Although several monoalkylchloroboranes have been prepared by the 1 1 reaction of an alkene with monochloroborane-diethyl ether (see Section 3.10.3.2), almost the only one to receive detailed investigation is thexylchloroborane. This reagent is most useful as its dimethyl sulfide complex, prepared according to equation (45)" or equation (46), ... 

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