[reaction: see text] In the presence of rhodium catalyst, (2-furyl)carbenoids generated from conjugated ene-yne-carbonyl compounds 1 efficiently undergo carbene transfer reactions with allylic sulfides followed by [2,3]sigmatropic rearrangement of sulfur ylides to give furan-containing sulfides in good yields. When diallyl sulfide is employed, heteroatom-containing polycyclic compounds are obtained
Catalytic thienylcarbene-transfer reactions have been developed. The rhodium-catalyzed reaction of alkenes, furans, and thiophenes with a thiocarbamoyl-ene-yne compound as a carbene source gave the cyclopropanation products or ring-opened products of heterocycles. These processes provide efficient synthetic methods for thiophene-containing complex molecules.
The reaction of alkenes with conjugated ene-yne-ketones, such as 1-benzoyl-2-ethynylcycloalkenes, with a catalytic amount of Cr(CO)5(THF) gave 5-phenyl-2-furylcyclopropane derivatives in good yields. The key intermediate of this cyclopropanation is a (2-furyl)carbene complex generated by a nucleophilic attack of carbonyl oxygen to an internal alkyne carbon in π-alkyne complex or σ-vinyl cationic complex
variety of alkenes in the presence of a catalytic amount of Cr(CO)(5)(THF) at room temperature gives (2-furyl)cyclopropanes in good yields. These cyclopropanation reactions proceed via (2-furyl)carbene-chromium intermediates 4 formed in situ from ene-yne-ketones 3. Late transition metals, such as [RuCl(2)(CO)(3)](2), [RhCl(cod)](2), PdCl(2), and PtCl(2), also catalyze effectively the cyclopropanation of styrene
novel palladium- and copper-catalyzedone-pot multicomponent synthesis of hetero α,α′-dimers of heterocycles via Sonogashira coupling and double cyclization cascade involving imine formation has been developed. This reaction cascade proceeded under mild conditions, providing a powerful synthetic tool for the assembly of π-conjugated systems with a combination of palladium-catalyzed post-direct C–H bond