2,2-Dimethyl-2-sila-1,4-dioxan and its derivatives having the formula FORM:0995394/C3/1 are prepared by reacting a dimethyl-(bromomethyl)-alkoxy- or chloro-silane with an equimolar amount of an organic compound containing two hydroxy groups on adjacent carbon atoms to form a dimethyl-(bromo-methyl)-(b hydroxy-organooxy)-silane and slowly adding to the latter at elevated temperature a tertiary nitrogen base in amount equivalent to the bromine. If a chlorosilane is used in the first reaction, a tertiary nitrogen base must also then be present in stoichiometric amount. The compounds other than 2,2-dimethyl-2-sila-1,4-dioxan itself are claimed per se. Examples of compounds with two adjacent hydroxy groups are ethylene glycol, pyrocatechol, 1,2-dihydroxy - 4 - alkoxybenzenes and 1,2-dihydroxy-4-(trifluoromethylmercapto benzene. Triethylamine is the preferred base. In the Examples: (1) 2,2 - dimethyl - 2 - sila - 1,4-dioxan is prepared via 1-hydroxy-2-[dimethyl-(bromomethyl) - siloxy] - ethane; (2) benzo - 2,2 - dimethyl - 2 - sila - 1,4 - dioxan is prepared via 1 - hydroxy - 2 - [dimethyl - (bromomethyl)-siloxy] - benzene; (4) (trifluoromethyl - mercaptobenzo) - 2,2 - dimethyl - 2 - sila - 1,4-dioxan is prepared together with the benzo derivative from a mixture of the corresponding hydroxy compounds. Specification 957,987 is referred to.
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