Catalysis

Acceptor

Yield (engineering)

Metallurgy

Materials science

Functional group

Biochemistry

Lewis acids and bases

Lewis acid catalysis

Stereochemistry

Polymer

Medicinal chemistry

Combinatorial chemistry

Physics

Organic chemistry

Sequence (biology)

Cycloaddition

Condensed matter physics

Insertion reaction

Chemistry

Ketene

Organic Letters

Donor-acceptor cyclopropanes were reacted under Lewis acid catalysis with 3-thioxocyclobutanones as surrogates for disubstituted thioketenes.A broad scope of 2-substituted tetrahydrothiophenes with a semicyclic double bond was obtained under mild conditions, with high functional group tolerance and in excellent yield.A sequence of a formal [3+2]-cycloaddition followed by a subsequent release of disubstituted ketene is postulated as the mechanism.To start our investigations, we used D-A cyclopropane 1a and 3-thioxocyclobutanone 2a as model substrates.Initial reactions were carried out in dichloromethane at 60 °C.Whereas AlCl3, MgI2 and Zn(OTf)2 as Lewis acid showed no conversion, product formation was observed with Sn(OTf)2 and Yb(OTf)3 in moderate yield (Table 1, entries 1-5).Subsequently, other common Lewis acids have been subjected to the reaction conditions, whereby Sc(OTf)3 seemed to be the most promising catalyst

Formal Insertion of Thioketenes into Donor–Acceptor Cyclopropanes by Lewis Acid Catalysis