Preparation of functionalized, in particular alkenylated, organomonoalkoxy-(or monohydroxy)-silanes

A process for preparing at least one functionalized organomonoalkoxy-(or monohydroxy)-silane of formula (I):

• in which:
• the symbol R1 is hydrogen or a monovalent hydrocarbon-based group selected from among a linear, branched or cyclic alkyl radical having from 1 to 20 carbon atoms and a linear, branched or cyclic alkoxyalkyl radical having from 1 to 20 carbon atoms;
• the symbols R2, which may be identical or different, are each a linear, branched or cyclic alkyl radical having from 1 to 8 carbon atoms, an aryl radical having from 6 to 18 carbon atoms, an arylalkyl radical or an alkylaryl radical (C6-C18 aryl, C1-C6 alkyl);
• R2 optionally bearing at least one halogenated or perhalogenated substituent;
• the symbol Y is a monovalent organic functional group, a functional group R3 comprising at least one site of ethylenic and/or acetylenic unsaturation, or is selected from among:
• linear, branched or cyclic alkenyl groups R3.1 having from 2 to 10 carbon atoms,
• linear, branched or cyclic alkynyl groups R3.2 having from 2 to 10 carbon atoms,
• linear, branched or cyclic -(alkenyl-alkynyl) or -(alkynyl-alkenyl) groups R3.3 having from 5 to 20 carbon atoms,
• wherein Y optionally comprises at least one heteroatom and/or bears one or more aromatic substituents;
• which process comprises:
• reacting at least one organoalkoxysilane (II), selected from among di-, tri- and tetraalkoxysilanes and mixtures thereof, with at least one halogenated organic compound (III) in the presence of at least one metal (M) and in the presence of at least one solvent (S1), said halogenated organic compound (III) being suited for substituting the alkoxy radicals with organic radicals, according to the following reaction scheme (reaction II/III):
• in which:
• the symbols R1, R2 and Y are as defined above;
• the symbol M is a metal selected from among Mg, Na, Li, Ca, Ba, Cd, Zn, Cu, mixtures thereof and alloys thereof:
• the symbol X is a halogen;
• and comprising the following steps:
• (a) contacting the metal M with the solvent S1, or optionally with a solvent S2;
• (b) optionally activating the reaction, whether by adding a catalytic amount of at least one halogen and/or an alkyl halide and/or by heating the reaction medium and/or the metal M;
• (c) adding the organoalkoxysilane (II) thereto;
• (d) adding thereto the halogenated organic compound (III), gradually and at a rate of introduction into the reaction medium lower than or equal to the rate of consumption of (III) in the reaction (II/III);
• (e) wherein the reaction (II/III) producing the reaction product (I), the temperature of the reaction medium optionally being maintained at a temperature θr less than or equal to the boiling point θb.p.S1 of the solvent S1;
• (f) optionally adding a solvent S2;
• (g) separating out and recovering a functionalized organomonoalkoxy-(or monohydroxy)-silane (I);
• (h) optionally filtering and optionally washing the filter cake thus obtained, or
• (h′) optionally dissolving the metal salts by washing with an acidic aqueous solution;
• and
• (i) optionally hydrolyzing the organomonoalkoxysilane (I) into an organomonohydroxysilane (I).