Organocatalytic Enantioselective Petasis-Type Reaction

In this pivotal example, the authors have demonstrated the ability of bifunctional thiourea organocatalyst 28 to provide the sufficient activation of organoboronic acids in the Petasis reaction using quinolones 26, as a powerful method for the enantio- and regioselective synthesis of 1,2-adducts 29 against the possibility of generation of 1,4-adducts (Table 4.1) [28], 

Schaus group reported a new organocatalytic enantioselective example of Petasis reaction employing chiral biphenol-derived diol 30 as effective catalyst to promote 

SCHEME 4.13 Multicomponent synthesis of trigonal prismatic cages 24. 

SCHEME 4.14 Petasis reaction using a-hydroxy aldehydes. 

Entry Substrate Boronic acid T(°C) Product (yield) ee (%) 

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The enantioselective, organocatalytic variant of the Petasis reaction, developed by Takemoto and coworkers from the University of Kyoto, represents a breakthrough in the synthesis of enantiopure 1,2-dihydroquinolines. As mentioned before, this structural unit is present in many natural products and biologically active compounds, and therefore an effective and short synthetic route via the Petasis-type reaction to enantiopure compounds in this class is a major leap forwards. Screening of the new thiourea catalysts in the Takamoto group resulted in a highly effective catalyst 13, specifically designed for the Petasis reaction. 

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