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

1982-05-24

1984-09-11

Siegel, Alan

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

Organic compounds

Sulfur containing

549374, 549375, 549453, 549454, 424275, C07C14900, C07D30700

Patent

active

044711395

ABSTRACT:
Processes for preparing isomerically 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: 3742063 (1973-06-01), Hagemeyer
patent: 4371708 (1983-02-01), Kramer
Wolinsky et al., J. Org. Chem. 29, 3740-3742 (1964).
Tilak, et al., Tetrahedron Letters No. 24, 1609-1612 (1964).
Parham et al., J. Am. Chem. Soc. 75, 2065-2069 (1953).
Fatiadi, Synthesis, Mar. 1976, pp. 133-136.
Minster et al., J. Org. Chem. 43, 1624-1626 (1978).
Evans et al., J. Org. Chem. 44, 497-501 (1979).

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