Processes for making 3-methylthiophene-2-carboxaldehyde and inte

Details Processes for making 3-methylthiophene-2-carboxaldehyde and inte Processes for making 3-methylthiophene-2-carboxaldehyde and inte

1984-02-17

1984-10-09

Siegel, Alan

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

424275, C07D33324, A61K 3138

Patent

active

044763123

ABSTRACT:
Processes for preparing isometrically pure 3-methylthiophene-2-carboxaldehyde, an intermediate for synthesis of anthelmintic agents, by reaction of mercaptoacetaldehyde or the dimer, or a polymer thereof, or a dialkylacetal thereof in the presence of a base with (1) methyl vinyl ketone or an alpha- or beta- oxidized derivative of methyl vinyl ketone to form a 3-oxobutylmercaptoacetaldehyde or dialkyl acetal thereof, or an alpha- or beta-substituted derivative thereof which is then converted to 3-methylthiophene-2-carboxaldehyde via appropriate steps including, if necessary, treatment with acid, followed, if necessary, by enamine catalyzed cyclization and, in the case of using methyl vinyl ketone as reactant, a dehydrogenation step; or (2) 3-butyn-2-one to produce a mixture of isomeric 3-oxobut-1-enylmercaptoacetaldehyde or dialkyl acetals thereof which is cyclized to 3-methylthiophene-2-carboxaldehyde.
A further aspect of this invention is an improved process for making dialkyl acetals of 2-mercaptoacetaldehyde which comprises reacting an alkyl vinyl ether with sulfur chloride to produce a bis(2-chloro-2-alkoxy ethyl)disulfide which is then treated with an alcohol to afford a bis(2,2-dialkoxyethyl)disulfide which is reduced under alkaline conditions to 2-mercaptoethyl acetaldehyde alkali metal salt which can be alkylated to a thioether, a valuable intermediate.

REFERENCES:
patent: 2601479 (1952-06-01), Weston
patent: 2853493 (1958-09-01), Weston

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