GB899558A - Improvements in or relating to chemical processes - Google Patents

Abstract

A process for carrying out reactions in which sodium borohydride is a reactant comprises using as a reaction medium a liquid, a minor proportion of which comprises one or more linear polyethers and a major component of which is a liquid in which sodium borohydride is substantially insoluble. The linear polyether may be derived from diethylene, triethylene and tetraethylene glycols or di-, tri- and tetra-1:2-propylene glycols, dialkyl ethers of diethylene glycol, e.g. the dimethyl ether, being preferred. Preferably the linear polyether constitutes 1-20% by weight of the major component. The major component may be more volatile than the linear polyether component and may have a boiling point below 120 DEG C. Specified major components are dimethyl ether, diethyl ether, tetrahydrofuran and tetrahydropyran and mixtures thereof, dioxan, hydrocarbons and halogenated hydrocarbons. If desired the reactants may be brought together in the liquid which is the major component and thereafter the linear polyether may be added thereto. In examples the use of sodium borohydride is described for the preparation of (1) diborane, (2) dichloroborane and (3) trimethylamine dichloroborane. Specification 873,267 is referred to.ALSO:A process for carrying out reactions in which sodium borohydride is a reactant comprises using as a reaction medium a liquid, a minor proportion of which comprises one or more linear polyethers and a major component of which is a liquid in which sodium borohydride is substantially insoluble. The linear polyether may be derived from diethylene, triethylene and tetraethylene glycols or di-, tri- and tetra-1 : 2-propylene glycols, dialkyl ethers of diethylene glycol, e.g. the dimethyl ether, being preferred. The major component of the liquid reaction medium may be a mono-ether, e.g. dimethyl or diethyl ether, tetrahydrofuran and tetrahydropyran, and mixtures thereof or dioxan or a hydrocarbon, such as a saturated aliphatic or aromatic hydrocarbon, or a petroleum fraction, or a halogenated hydrocarbon. Specified reactions involving sodium borohydride are (1) with boron trifluoride to produce diborane, (ii) with the appropriate quantity of boron trichloride to give etherates of partially chlorinated boranes and (iii) those reactions involving esters, aldehydes, ketones and ethylenic compounds. Examples describe the use of sodium borohydride to produce dichloroborane etherate which is reacted with trimethylamine to give trimethylamine dichloroborane. Specification 873,267 is referred to.