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Phosphine-initiated general base catalysis: facile access to benzannulated 1,3-diheteroatom five-membered rings via double-Michael reactions of allenes.

ABSTRACT: General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excellent yields. Careful mechanistic studies unveiled the phosphine-triggered general base catalysis pathway. Furthermore, the double-Michael reaction can serve as an alternative method for the selective monoketalization of ?-diketones.

SUBMITTER: Szeto J

PROVIDER: S-EPMC3193576 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Phosphine-initiated general base catalysis: facile access to benzannulated 1,3-diheteroatom five-membered rings via double-Michael reactions of allenes.

Szeto Judy J Sriramurthy Vardhineedi V Kwon Ohyun O

Organic letters 20110920 20

General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excel ...[more]

PMID: 21932819

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