Synthesis of 1,2-Disubstituted Cyclopentenes by Palladium-Catalyzed Reaction of Homopropargyl-Substituted Dicarbonyl Compounds with Organic Halides via 5-Endo-Dig Cyclization

Abstract

Palladium catalysts with bulky biaryl phosphine ligands allow homopropargyl-substituted dicarbonyl compounds to undergo intramolecular addition via a rare 5-endo-dig pathway. C-C bond forming reductive elimination follows the addition to introduce alkenyl and alkynyl as well as aryl groups by using the corresponding organic halides. The cyclization is versatile enough to be applicable to the synthesis of highly substituted dihydropyrrole and a fused tricyclic compound.

Chemicals from Alkynes with Palladium Catalysts

“…128 In addition, this type of 5-endo-dig carboannulation is observed in arylative cyclizations leading to indenes, with structurally limited substrates activated by the conjugation of the aromatic ring. 129 An example of this last process is represented in Scheme 49, where 2-[2-(2-phenylethynyl)phenyl]malonate (126) is cyclized in the presence of an aryl or vinyl halide such as phenyl iodide under Pd(PPh 3 ) 4 catalysis (5 mol%) and potassium carbonate as base in DMF at 100 ºC, affording indene 127.…”

Formal anti‐Carbopalladation Reactions of Non‐Activated Alkynes: Requirements, Mechanistic Insights, and Applications

“…To exclude a nucleopalladation [9][10][11] by the second triple bond one alkyne moiety was replaced with an alkene resulting in enynes (Z)-6 and (E)-6 exhibiting different double bond geometries (Scheme 4). Exposing these substrates to our reaction conditions, enyne (Z)-6 delivered 7 a and (E)-6 delivered diene 7 b, exclusively.…”

Pd-catalyzed intramolecular addition of active methylene compounds to alkynes with subsequent cross-coupling with (hetero)aryl halides

“…Dimethyl (2E)-2-(naphthalen-2-ylmethylidene)cyclopentane-1,1-dicarboxylate (9) Prepared in reaction of dimethyl 4-pentenylmalonate and 2bromonaphthalene following general procedure (90 mg, yield 69%). Product was isolated as oil aer column chromatography on silica gel (15 g, hex/AcOEt 90 : 10).…”