Palladium-Catalyzed Asymmetric Sequential Hydroamination of 1,3-Enynes: Enantioselective Syntheses of Chiral Imidazolidinones

Abstract

Pd-catalyzed sequential hydroamination of readily available 1,3-enynes is reported. The redox-neutral process provides an efficient route to synthesize a broad scope of imidazolidinones, thiadiazolidines, and imidazolidines. Asymmetric sequential hydroamination generates a series of synthetically valuable, enantioenriched imidazolidinones. Mechanistic studies revealed that the transformation occurred via an intermolecular enyne hydroamination pathway to give an allene intermediate. Subsequent intramolecular hydroamination of the allene intermediate proceeded under the Curtin–Hammett principle to provide enantioenriched imidazolidinone products.

Recent Advances in the Synthesis of Five‐membered Nitrogen Heterocycles Induced by Palladium Ions and Complexes

“…Li, Yao et al . have explored the sequential hydroamination of readily available 1,3‐enynes with varied amine sources to construct hydantoins [43] . Upon screening catalyst systems, [Pd(allyl)Cl] 2 and Xantphos in combination with triphenylmethyl carboxylic acid additive were found to give the best performance.…”

“…[42] Li, Yao et al have explored the sequential hydroamination of readily available 1,3-enynes with varied amine sources to construct hydantoins. [43] Upon screening catalyst systems, [Pd-(allyl)Cl] 2 and Xantphos in combination with triphenylmethyl carboxylic acid additive were found to give the best performance. Reactions of 1,3-enynes with 1,3-disubstituted ureas furnished a wide range of substituted imidazolidin-2-ones (31 examples, 30-85 %) including a 4-estrone-substituted derivative with a yield of 74 %.…”

Umpolung Asymmetric 1,5‐Conjugate Addition via Palladium Hydride Catalysis

“…Recently, considerable progress has been achieved in transition metal‐catalyzed asymmetric hydrofunctionalizations [22, 23] of conjugated dienes [24–48] . We thus envisioned that the long‐time unsolved umpolung nucleophilic 1,5‐addition might be realized if suitably defined palladium hydride catalysis [49–60] was identified (Scheme 1b). However, classical hydrofunctionalizations of conjugated dienes are limited to the use of inert aryl and alkyl units as substituents [22–48] .…”

Cascade Multicomponent Assemblies Involving 1,3-Enynes via Auto-Tandem Palladium Catalysis

“…Over the past few decades, fruitful difunctionalization reactions of 1,3-enynes have been developed by employing metal, organo, and cooperative catalysis . Except for radical pathways, transition metal-catalyzed difuctionalization of 1,3-enynes usually involved the insertion of organometallic species into the olefin terminus to generate propargylic or allenyl intermediates, which were then captured by various electrophiles or nucleophiles to produce structurally diversified 1,2- or 1,4-addition products. , On the contrary, certain organometallic species, especially metallic hydrides, tended to add to the triple bond first, and 1,4-addition products were produced after subsequent transformations (Scheme a) …”