Highly Enantioselective Nitro-Mannich Reaction Catalyzed by Cinchona Alkaloids and N-Benzotriazole Derived Ammonium Salts

Abstract

The catalytic enantio- and diastereoselective nitro-Mannich reaction of α-amido sulfones in the mixed solvent of toluene/H(2)O has been realized using a phase-transfer catalyst (PTC) derived from cinchona alkaloids and N-benzotriazole. It performed well over a wide range of substrates to give the desired products in good yields (up to 94%) with excellent enantioselectivities (up to 99% ee) and diastereoselectivities (up to 99:1).

Recent Developments in Asymmetric Phase‐Transfer Reactions

“…The unprotected hydroxy group on N-benzylquininium chloride 2 l was found to be crucial to obtain high enantioselectivities. Other types of cinchona alkaloid derived phase-transfer catalysts such as 2 m [117] and 1 m [118] were subsequently applied to the reaction to give products with high enantioselectivity (Scheme 91).…”

Imine and iminium precursors as versatile intermediates in enantioselective organocatalysis

“…53 They made the interesting observation that the enantioselectivity of the reaction was completely reversed by changing the alkyl group of quaternary ammonium from benzyl to an N-benzotriazole derivative, in spite of using quinine as the scaffold like Palomo, Herrera, and Kuramaswamy. In their hands, the addition of nitromethane or nitroethane to N-Boc-amidosulfones catalyzed by 27 proceeded smoothly in low temperatures to give the products in good to excellent yields and enantioselectivities (Scheme 30).…”

Neue Entwicklungen bei asymmetrischen Phasentransferreaktionen

“…Die ungeschützte Hydroxygruppe des N-Benzylchininiumchlorids 2 l war ausschlaggebend für den Erhalt hoher Enantioselektivitäten. Auf der Grundlage dieser Arbeiten wurden auch die von Cinchona-Alkaloiden abgeleiteten Phasentransferkatalysatoren 2 m [117] and 1 m [118] in der Reaktion verwendet und ergaben die Produkte mit hohen Enantioselektivitäten (Schema 91).…”