Enantioselective Michael Addition of Nitroalkanes to Nitroalkenes Catalyzed by Chiral Bifunctional Quinine‐Based Squaramides

Abstract

Af amilyo fc hiral bifunctional acid-/base-type quinine/squaramide organocatalysts is shown to be highly active promoters of the conjugate addition of 1-nitropropane to various trans-b-nitroalkenes.T he cooperation of the quinine and the sterically encumbered squaramide moieties catalyzed the Michael addition reactions at 0 8Cb yu sing ac atalyst loading of only 2mol %t oa fford the 1,3-dinitro Michael adducts with excellent enantioselectivity and diastereoselectivity (up to 95 % ee and syn/anti isomers up to 96:4).

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

“…We have previously reported the synthesis of new amino-substituted-DMAP-based sulfonamides [ 39 ] and quinine-based squaramide-type organocatalysts [ 40 ]. Motivated by the excellent results obtained with our aforementioned catalysts, we developed a new chiral bifunctional sulfonamide–quinine organocatalyst that unites both classes.…”

“…Motivated by the excellent results obtained with our aforementioned catalysts, we developed a new chiral bifunctional sulfonamide–quinine organocatalyst that unites both classes. The synthesis of the basic part was initiated by converting quinine to quinineamine via a Mitsunobu reaction, followed by a Staudinger reduction [ 40 ]. Then it was coupled with the acidic part, which was obtained by the nitration of 2,4,6-trimethylbenzenesulfonyl chloride [ 39 ] to obtain organocatalyst 5 ( Scheme 1 ).…”

The Synthesis of Chiral β-Naphthyl-β-Sulfanyl Ketones via Enantioselective Sulfa-Michael Reaction in the Presence of a Bifunctional Cinchona/Sulfonamide Organocatalyst

“…We have previously reported the synthesis of new aminoDMAP based sulfonamides [18] and quinine based squaramide-type organocatalysts [19]. Motivated by the excellent results obtained with our aforementioned catalysts, we developed a new chiral bifunctional sulfonamide/quinine organocatalyst, which unites both classes.…”

Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

“…A chiral bifunctional alkaloid-squaramide organocatalyst 131 has been used for the Michael addition of 1-nitropropane to different nitroalkenes [ 142 ]. The conjugate addition products 132 were obtained in high to excellent yields and stereoselectivities, being insensitive to the electronic nature of the aromatic ring ( Scheme 35 ).…”