DE1643268A1 - Process for the preparation of 1,3-thioxolanes - Google Patents

Description

Process for the preparation of 1,3-th.ioxolanes The subject of this invention is a process for the preparation of 1,3-th.ioxolanes by. Treatment of vinyl-ß-hydroxyethyl sulfides with acidic catalysts.

It is known that 1,3-Th.ioxolane in the conversion of aldehydes or ketones with ß-hydroxyethyl mercaptan are formed at elevated temperatures (GDR patent document 53,703; Journal of the American Chemical Society, Volume 71, page 3555 (1949)). Even. Th.iodiglycol alone can condense to 2-methyl-1,3-th.ioxolane in the presence of alkali (Canadian Journal of Chemistry, Volume 37, page 1104 (1959)). Both procedures deliver the end products mentioned only in poor yield and on a cumbersome basis Ways.

It has now been found that 1,3-th.ioxolanes of the general formula in the R1 and R2 the same. or can be different and in each case denote hydrogen or an aliphatic radical, and also R1. can denote an aromatic radical is advantageously obtained when vinyl-ß-h.ydroxyäthylsulfide of the general formula treated with acidic catalysts.

The implementation can. in the case of the use of vinyl ßhydroxyäthylsulfid by. reproduce the following formulas: ._.: Procedure according to. the invention provides in comparison. to the known processes 1,3-th.ioxolane in a simple way, in better yield and without significant formation of by-products.

The vinyl-ß-hydroxyäth.ylsulfide used as starting materials 2I is easy to get through. Vinylation of the corresponding ß-hydroxyäth.ylmercaptans. Raw materials II and accordingly preferred end products I are those in their formulas R1 and R2 same. or can be different and each is hydrogen or an alkyl radical with 1 to 10, in particular 1 to ¢, carbon atoms, in addition R1 even. can denote an aryl radical with 6 to 10 carbon atoms.

For example, the following vinyl-ß-hydroxyä-th.ylsulfide can be used as starting materials II: Vinyl-ß-hydroxypropyl- or -butyls-Lfid; Vinyl-β-li (Iroxyl-itl) ylsilfid un-d # selne in the cK position to the u Z, sulfur atom on the hydroxylethyl radical by a methyl, butyl, octyl, phenyl or naphthyl group substituted homologues; corresponding vinyl-B-hydroxyethyl sulfides substituted on the hydroxyethyl radical in the "-" and 13-positions.

The reaction is carried out in the presence of acidic catalysts, preferably salts of a weak base with a strong acid. In particular, such salts are chlorides or sulfates of metals of the 1st, 2nd, B. subgroup and 3rd main group of the periodic table, for example copper sulfate, zinc sulfate, nickel sulfate, aluminum chloride, iron chloride or sulfate, cobalt sulfate. The salts are generally used in a concentration of 0.1 to 5, preferably 0.5 to 2 mol%, based on the starting material. Preferred catalysts are also. inorganic or organic acids, e.g. sulfuric acid, hydrochloric acid, phosphorus acid, sulphurous acid, ° ä eel °, ue,.: i @ Tsäure, ChloressigsäFare, Formic acid, chlorobenzoic acid 9 @. @@: @ _ @ lfsa @@. Acid 9 O @ s 1 @? ° e, Carbonic acid. They are generally in a range from 0.5 to 3 Moljo, based on the starting material, added. One can also. Use mixtures of these catalysts, for example silica gels impregnated with phosphoric acid as fixed bed or vortex contacts. Even. Acid ion exchangers can be used as catalysts, for example polystyrene sulfonic acid, phenol sulfonic acid, 3tyrene phosphinic acid, styrene phosphinic acid, resorcinol resins, aliphatic or aromatic carboxylic acid resins. The ion exchangers are used in an amount corresponding to the number of their exchange-active groups. The reaction is generally discontinuous at a temperature between 0 and 400 ° C., preferably between 50 and 200 ° C., without pressure or under pressure. or preferably continuously. carried out. The reaction can be carried out as follows: A mixture. starting material and catalyst are kept at the reaction temperature for 0.2 to 1 hour with thorough mixing. The end product is then separated off in a customary manner, for example by. fractional distillation of the reaction mixture under reduced pressure.

The mode of operation is preferably designed continuously the catalyst and some of the starting materials are initially introduced, continuously. further Adding starting material and at the same time distilling off the end product formed.

The after. the process of the invention, i.e., preparable compounds are valuable intermediate products for the production of dyes and herbicides.

The parts mentioned in the examples are parts by weight. Example 1 In a stirred vessel with a distillation attachment 20 parts Vinylß-h.ydroxyäth.ylsulfid and 1 part of copper sulfate (anhydrous) are charged and heated to 850C. With stirring, 500 parts of vinyl-β-hydroxyethyl sulfide per hour are slowly added at this temperature and 2-meth-yl-1,3-thioxolane formed at the same time is distilled off in vacuo at 100 torr. 484 parts (93% of theory) of the end product are obtained as a colorless, easily mobile liquid with a boiling point of 100-68 ° C., nD0 = 1, 4855.

Example 2 As described in Example 1, 20 parts of vinyl-β-hydroxyethyl sulfide and 2 parts of Levatit® - S 100 are placed in a reaction vessel and heated to 100.degree. While stirring, 500 parts of vinyl-β-hydroxyethyl sulfide per hour are slowly added at this temperature and 2-meth.yl-1,3-th.ioxolane which is formed at the same time is distilled off in vacuo at 100 torr.

494 parts (95% of theory) of the end product are obtained as a colorless, light weight movable liquid of Kp100_ = 68'C, n30 = 1.4855. registered trademark

Claims (1)

Claim. Process for the preparation of 1,3-thioxolanes of the general formula in which R1 and R2 can be identical or different and each denotes hydrogen or an aliphatic radical, and also R1. can denote an aromatic radical, thereby. marked lines, DAB one vinyl-.beta.-hydroxyäthylsulfide of the general formula treated with acidic catalysts.