Microwave-assisted solid-phase organic synthesis of substituted naphthols and trisubstituted olefins
A new method for the solid-supported synthesis of highly substituted naphthol derivatives involving Dötz benzannulation, triflation, and Suzuki cross-coupling reaction is described. The microwave-assisted Dötz benzannulation of resin-bound Fischer carbene complex with various alkynes afforded the corresponding resin-bound naphthol derivatives. The oxidative cleavage of this resin-bound product using CAN affords 1,4-napthoquinone derivatives in moderate yields. The triflation of these resin-bound naphthols with 4-nitrophenyltriflate, followed by the palladium-catalyzed Suzuki cross-coupling reaction of the resulting resin-bound naphthelenyl triflates and subsequent TFA cleavage produces the corresponding substituted naphthol derivatives in moderate yields. ^ The synthesis of 4-subsituted-1-naphthol derivatives involving the mono protection of 1,4-naphthols with trityl chloride resin, triflation and Suzuki cross-coupling followed by acid cleavage with TFA afforded 4-subsituted-1-naphthol derivatives with moderate yields is also described. In the progress of the project a new deborylation of boronic acid is achieved by the palladium-catalyzed reaction of PL-Wang-Br resin with boronic acid. A plausible catalytic cycle is proposed to account for the deborylation reaction. ^ In the progress of the project a new method for synthesizing solid-supported naphthols using three-component coupling reaction of resin-bound propargyl amine, aryl iodide, and boronic acid is also reported. A possible explanation is given for the initial failure of this three component coupling reaction. ^
Kongara, Sandeep, "Microwave-assisted solid-phase organic synthesis of substituted naphthols and trisubstituted olefins" (2005). ETD Collection for University of Texas, El Paso. AAI1434071.