title: 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 β-diketones.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, USA.
authors.forename: Judy
authors.initials: J
authors.lastname: Szeto
authors.forename: Vardhineedi
authors.initials: V
authors.lastname: Sriramurthy
authors.forename: Ohyun
authors.initials: O
authors.lastname: Kwon
mesh_terms: D000466:Alkadienes / Q000737:chemistry*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010720:Phosphines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000466:Alkadienes; D006571:Heterocyclic Compounds; D010720:Phosphines; C025947:propadiene; C049750:trimethyl phosphine