An Au(i)-catalyzed rearrangement/cyclization cascade toward the synthesis of 2-substituted-1,4,5,6-tetrahydrocyclopenta[b]pyrrole

Asymmetric Construction of Functionalized Cyclopenta[b]pyrrolines via Cascade Aza-Piancatelli/Hydroamination Reactions

A chiral Brønsted acid/Pd that cooperatively catalyzed the asymmetric cascade aza-Piancatelli rearrangement/hydroamination of readily accessible alkynyl-functionalized tertiary furylcarbinols with anilines has been developed. This protocol provides expedient access to a variety of densely functionalized cyclopenta[b]pyrroline derivatives in high yields with excellent enantioselectivities.

Hydrogen bonding-promoted tunable approach for access to aza-bicyclo-[3.3.0]octanes and cyclopenta[b] pyrroles

A unified strategy is disclosed that builds on successfully engaging the aniline nitrogen of 1,3-amphoteric γ-aminocyclopentenone for a tandem annulation with electron-poor alkynes, solely assisted by the H-bonding network of HFIP. This metal-free mild strategy provides access to medicinally relevant aza-bicyclo-octanes en route to another important scaffold: cyclopenta[b]pyrrole.

Synthesis of Pyrrole via Formal Cycloaddition of Allyl Ketone and Amine under Metal-Free Conditions

A new metal-free synthesis of pyrrole from allyl ketone and amine has been established. The reaction proceeds via an thiolative activation of the C-C double bond with dimethyl(methylthio)sulfonium trifluoromethanesulfonate, followed by a nucleophilic ring-opening addition of primary amine to the generated episulfonium intermediate, and then an internal condensation and aromatization. This mild procedure provides a novel strategy to the construction of substituted pyrroles through a formal [4 + 1] cycloaddition reaction.

Gold(I)-Catalyzed Synthesis of Highly Substituted 1,4-Dicarbonyl Derivatives via Sulfonium [3,3]-Sigmatropic Rearrangement

An efficient and straightforward gold-catalyzed protocol for the synthesis of 2-substituted 4-oxo-4-arylbutanal derivatives from commercially available or easily accessible alkynes and vinylsulfoxide substrates has been developed. Extension of the methodology to the use of 1-cycloalkenyl sulfoxides allowed the facile synthesis of five-, six-, and seven-membered-ring cycloalkyl-1-one backbone. Subsequently, the tetrahydrocycloalkyl[b]pyrrole derivatives, which are found in many active pharmaceutical ingredients, were isolated in good yields. Mechanistic investigation highlighted a [3,3]-sigmatropic rearrangement of a sulfonium intermediate in this process.

Brønsted Acid-Catalyzed Formal [2 + 2 + 1] Annulation for the Modular Synthesis of Tetrahydroindoles and Tetrahydrocyclopenta[ b]pyrroles

An expedient synthesis of tetrahydroindoles and tetrahydrocyclopenta[ b]pyrroles, highlighted by Brønsted acid catalyzed formal [2 + 2 + 1] annulation reaction, is reported. Using three readily accessible reaction components, i.e., an electrophilic species in silyloxyallyl cations and two distinct nucleophiles in silylenol ethers and amines, our chemistry enables the assembly and functionalization of these biologically important N-heterocycles in a highly modular manner.

Copper-catalyzed cyclization of 2-cyanobenzaldehydes and 2-isocyanoacetates: an efficient strategy for the synthesis of substituted 1-aminoisoquinolines

An efficient strategy for the synthesis of substituted 1-aminoisoquinoline has been developed.

A diversity-oriented synthesis of cyclopenta[b]pyrroles and related compounds through a calcium(ii)/copper(ii) catalytic sequence

A sequential bicatalytic route relying on calcium(ii) and copper(ii) salts is described to provide access to original nitrogen-containing heterocycles.

Ammonium Acetate-Promoted One-Pot Tandem Aldol Condensation/Aza-Addition Reactions: Synthesis of 2,3,6,7-Tetrahydro-1H-pyrrolo[3,2-c]pyridin-4(5H)-ones

An efficient tandem intermolecular one-pot aldol condensation/aza-addition reaction of 2-methyl-3-carbamoylpyrroles and aldehydes was developed for the synthesis of 2,3,6,7-tetrahydro-1H-pyrrolo[3,2-c]pyridin-4(5H)-ones. The reaction proceeded using only 3.0 equiv of ammonium acetate promoter in green solvent poly(ethylene glycol)-400 at 100 °C to afford a series of pyrrolo[3,2-c]pyridinone derivatives in good to excellent yields.

Gold-catalyzed tandem cycloisomerization/Petasis–Ferrier rearrangement: a direct route to 3-alkoxyindanones from enynals and alcohols

A method to prepare 3-alkoxyindanones by gold-catalyzed tandem cycloisomerization/Petasis–Ferrier rearrangement of ortho-ethynylarylaldehydes with alcohols is described. The reaction also offers a synthetic route to 3-alkoxylcyclopentenones.