An improved route to substituted cyclopenta[c]thiophenes was accomplished by treating 1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene-5-one (1) with alkyl Grignard reagents to obtain the 5-alkyl-1,3-dimethyl-4H-cyclopenta[c]thiophenes, 5-methyl-1,3-dimethyl-4H-cyclopenta[c]thiophene (2) and 5-ethyl-1,3-dimethyl-4H-cyclopenta[c]thiophene (3), in good yield (60% and 65%, respectively). An important cyclopenta[c]thiophene precursor, 5-carbomethoxy-5-phenylsulfonyl–1,3-dimethyl-5,6-dihydro-4H-cyclopenta[c]thiophene (9) was synthesized, in an alternate route, by treating 3,4-bis(chloromethyl)-2,5-dimethylthiophene (7) with methyl phenyl sulfonyl acetate (8).
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1 March 2009
An Improved Route to Substituted Cyclopenta[c]thiophenes: Synthesis of 5-Alkyl-1,3-dimethyl-4H-cyclopenta[c]thiophenes and Sulfone Ester Precursor
Chad A. Snyder,
Amber J. Bell,
Vineet V. Karambelkar,
Joseph B. Scott,
Riley G. Jones,
Paul J. Orosz,
Jessica M. Wilson,
Nathan C. Tice
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Journal of the Kentucky Academy of Science
Vol. 70 • No. 1
Spring 2009
Vol. 70 • No. 1
Spring 2009
Cyclopenta[c]thiophene
Grignard
heterocycles
methyl phenyl sulfonyl acetate
thiapentalene