Synthesis of Alkynylcyclopentenols on a Foam-Supported Palladium Catalyst

Key words

palladium catalysis - domino reaction - enallenes - carbocyclization - alkynylation - cyclopentenols

Significance

Palladium(II) immobilized on an aminopropyl-functionalized siliceous mesocellular foam (Pd^II-AmP-MCF) catalyzed the oxidative carbocyclization/alkynylation reaction of enallenes 1 with terminal alkynes in the presence of benzoquinone and triethylamine in DCE to give the corresponding alkynylcyclopentenols 2 in up to 85% yield with >20:1 diastereoselectivity and >99% ee (eq. 1; 19 examples). Pd^II-AmP-MCF also promoted the oxidative carbocyclization/borylation of enallene 1k with bis(pinacolato)diboron to afford enol 3 in 89% yield (eq. 2).

Comment

In the reaction of 1a with ethynylbenzene, the catalyst was recovered by centrifugation and reused six times without loss of its activity. The authors have previously reported the preparation of Pd^II-AmP-MCF and its application in oxidative cascade reactions for the formation of cyclobutenols, γ-lactones and γ-lactams, and furans (Chem. Eur. J. 2019, 25, 210; J. Am. Chem. Soc. 2018, 140, 14604; Angew. Chem. Int. Ed. 2020, 59, 1992).

Publication History

Article published online:
18 March 2021