Process for the preparation of methyl 1,1-dichloromethyl ether or of ethyl 1,1-dichloromethyl ether

Process for the preparation of methyl 1,1-dichloromethyl ether or of ethyl 1,1-dichloromethyl ether, characterized in that methyl formate or ethyl formate is reacted with phosgene, diphosgene, triphosgene or oxalyl chloride, or one of their mixtures, at a temperature of between 40.degree. C. and 100.degree. C., in the presence of a catalyst chosen from the group consisting of:

• the trisubstituted phosphine oxides and sulphides of general formula (I) ##STR8## in which X denotes an oxygen or sulphur atom and R.sup.1, R.sup.2 and R.sup.3, which are identical or different, denote a substituted or unsubstituted aromatic radical,
• the trisubstituted phosphine dichlorides of general formula (II) ##STR9## in which R.sup.1, R.sup.2 and R.sup.3 have the abovementioned meaning, the formamides of general formula (III) ##STR10## in which each of R.sup.4 and R.sup.5, which are identical or different, denotes a C.sub.4 -C.sub.10 aliphatic radical or a cyclohexyl radical,
• the products of reaction of the formamides of formula (III) with chlorinating agents,
• and mixtures thereof.