1.2- Dichloroethyl ethyl ether

In 1911 Benary reported a modification of Feist s original procedure. He reacted chloroacetaldehyde (8), generated in situ from the ammonia promoted decomposition of 1,2-dichloroethyl ethyl ether (7), with ethyl acetoacetate (9) and ammonia to yield ethyl 2-methyl 3-furoate (10). ... 

Several significant pyrrole syntheses involve the formal tricomponent cyclization of type III ace (equation 126). The Hantzsch pyrrole synthesis involves a dicarbonyl compound, an a -halo ketone and ammonia or an amine. The mechanistic pattern is similar to that involved in the Knorr synthesis (Section 3.06.3.4.1). In addition to a-halo ketones and a-haloal-dehydes, compounds such as 1,2-dichloroethyl acetate, 1,2-dibromoethyl acetate and 1,2-dichloroethyl ethyl ether can serve as a -haloaldehyde equivalents (equation 127) (70CJC1689, 70JCS(C)285>. It is believed that the initial step in these reactions is the formation of a stabilized enamine from the amine and the /3 -dicarbonyl compound. A structural ambiguity... 

In the preparation of 1,2-dichloroethyl ether from diethyl ether516 care must be taken to cool the mixture in ice-water in the early stages and to introduce the chlorine slowly, since accumulation of chlorine easily leads to a violent reaction in which the mixture catches fire. As the reaction proceeds, the mixture becomes saturated with HC1, whereby the flammability is reduced. However, unless the stirring is rapid, the solution can become supersaturated with HC1 which is then later released with violence. Chlorination of diethyl ether (800 g), first with ice-cooling (35 h to a density of 0.785), then at temperatures rising gradually to room temperature (a further 47 h to a density of 0.96), gave 24.2% of 1,2-dichloroethyl ethyl ether. 

Under certain conditions tt,/ -dichloro ethers (cf. page 170) react as a mixture of chloroacetaldehyde, alcohol, and HC1, e.g., in the synthesis of 2-amino-thiazole from 1,2-dichloroethyl ethyl ether and thiourea in water. 

Simple examples of this strategy, which for the synthesis of thiazoles is known as the Hantzsch synthesis, are shown below the syntheses of 2,4-dimethylthiazole where the heteroatoms are provided by thioacetamide, " and 2-aminothiazole, in which 1,2-dichloroethyl ethyl ether is utilised as a synthon for chloroethanal and the heteroatoms derive from thiourea. " The use of thioureas as the sulfur component with 2-chloroacetamides as the second unit gives rise to 2,4-diaminothiazoles. " Conversion of 1,3-diketones into their 2-phenyliodonium derivatives and reaction of these with thioureas produces 2-amino-5-acylthiazoles. The first step in such ring syntheses is 5-alkylation. " A useful variant is the use of an a-diazo ketone in place of the a-halocarbonyl component. " ... 

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