4 years ago

Asymmetric Squaramide Catalyzed Domino aza-Friedel-Crafts/N,O Acetalization Reactions Between 2-Naphthols and Pyrazolinone Ketimines

Kari Rissanen, Arto Valkonen, Kristina Deckers, Suruchi Mahajan, Pankaj Chauhan, Ugur Kaya, Dieter Enders
Pyrazolin-5-one derived N-Boc ketimines have been explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel protocol requires only a catalyst loading of 0.5 mol% of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98%) and stereoselectivities (>99:1 dr and 97-98% ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98% yield and 47-98% ee.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/anie.201709224

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