Monochloroborane,

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). 

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. 

Antoine constants, 6 215t chlorocarbon/chlorohydrocarbon of industrial importance, 6 227t toxocity, 6 2181 uses, 6 222-223 Monochloroborane, 73 636 a-Monochlorobutanoic acid (MBA),... 

Functionalised 2,3-dihydro-l,4-dioxins can be synthesised in a three step-sequence from P-keto esters. The key step is the insertion of a Rh-carbenoid derived from an a-diazo-p-keto ester into an 0-H bond of a 13-diol <99H(51)1073>. The reaction of 2-(l,4-dioxenyl)alkanols with silyl enol ethers yields 23-disubstituted 1,4-dioxanes. When 13-bis(trimethylsilyloxy)-cyclobut-l-ene is used, the expected cyclobutanone products are accompanied by a spirocyclopropane derivative <99TL863>. 1,4-Dioxane-monochloroborane 57 is a highly reactive hydroborating reagent <990L315>. 

Bicyclo[3.3 l]nonan-9-one, (2,4-dinitrophenyl)hydrazone (8,9) (—) Monochloroborane diethyletherate Borane, chloro-, compound with ethyl ether (8), Borane, chloro-, compound with 1,1 -oxybis[ethane] (1 1) (9) (36594-41-9). 

MIDETR1ETHYLAMINE, 58, 122 Methyl thiohenzoate, 58, 41,43 Methyl vinyl ketone, 58, 162, 163, 164, 167 Moffat oxidation, 56, 99 Monochloroborane dicthylctherate, 58,... 

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. 

Hydroboration. Monochloroborane in ethyl ether hydroborates a wide variety of olefins to give the corresponding dialkylchloroborancs in high yield ... 

HYDROBORATION Bis(3,6-dimethyl)bore-pane. Bis(tni7ni-2-methylcyclohexyl)bo-rane. Catecholborane. Dicyclohexylbo-rane. Diisopinocamphenylborane. 2,3-Dimethyl-2-butyIborane. Dimethyl sul-fide-Borane. Monochloroborane-Diethyl ctherate. 

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]. 

The early literature associated with monochloroborane hydroborations contains errors and it is probably appropriate to ignore publications prior to about 1970. Monochloroborane complexes THE more strongly than does borane and this slows down its reactions with alkenes in this solvent. Thus, other reactions may compete and mixtures may result. The diethyl ether complex is weaker and hydroborations... 

The reactions of monochloroborane in diethyl ether with a,(o-dienes lead initially to mixtures which are partially polymeric and possibly composed of different ring sizes. However, careful distillation can lead to both depolymerization and isomerization, so that in several cases a single cyclic product can be obtained (e.g. Scheme 5). ... 

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), ... 

The hydroboration of dichloromethylvinylsilane in Eq. 1 was performed with borane-dimethylsulfide dissolved in toluene in a molar ratio of 3 1 at 0-10°C to exclude side reactions [7], The first and second additions take place with high a-stereoselectivity, caused by a negative partial charge at the a-C-atom [8], The third addition in Eq. 1 occurs in 3-position due to steric hindrance at boron. In order to obtain polymer 2 we added monochloroborane-dimethylsulfide in toluene to dichloromethylvinylsilane under the same reaction conditions as for 1, apart from a change in the molar ratio from 3 1 to 2 1 (Eq. 2). 

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... 

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