Dual reactivity pattern of allenolates "on water": the chemical basis for efficient allenolate-driven organocatalytic systems.
A study of the reactivity pattern associated with zwitterionic allenolates "on water" is reported. This study establishes the chemical basis for two organocatalyzed allenolate-driven reaction networks operating "on water". The first one is a chemodifferentiating three building block (ABB') three-component reaction (ABB' 3CR) manifold comprising terminal alkynoates and aldehydes. The manifold produces propargylic enol ethers 3 with higher average efficiency than their homologues in organic solvents. The second one is a novel organocatalytic system elicited by the reaction of alkynoates and nitrones in the presence of tertiary amines or phosphines. While terminal alkynoates afford 2,3,5-trisubstituted 2,3-dihydroisoxazoles 5 and propargylic N-hydroxylamines 6, internal alkynoates selectively afford the 2,3,4,5-tetrasusbstituted 2,3-dihydroisoxazaole 10. Importantly, in both cases, the 2,3-dihydroisoxazole ring is obtained as a sole regioisomer.
González-Cruz
David
D
Instituto de Productos Naturales y Agrobiología, Consejo Superior de Investigaciones Científicas, Astrofísico Francisco Sánchez 3, 38206 La Laguna, Tenerife Canary Islands, Spain.
Tejedor
David
D
de Armas
Pedro
P
García-Tellado
Fernando
F
D000480:Alkynes / Q000737:chemistry; D002384:Catalysis; D009281:Naphthalenes / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*
D000480:Alkynes; D009281:Naphthalenes; D009589:Nitrogen Oxides; C015388:nitrones; D014867:Water; C110055:allenolic acid