Asymmetric Formal Abnormal Claisen Rearrangement Enabled by Rh-Catalyzed Regio- and Enantioselective Allylic Alkylation

Abstract

Abnormal Claisen rearrangement of phenyl allyl ether with the γ-alkyl group is longstanding. However, the asymmetric version of this named reaction has never been reported. Herein, a highly regio-and enantioselective allylic alkylation of 4-hydroxycoumarin and stereospecific Conia-ene/ene sequence has been developed as a formal abnormal Claisen rearrangement. Chiral 4-hydroxycoumarins with 3-allyl groups could be synthesized in up to 95% yield and 96% ee under the catalysis of Rh and chiral bioxazolinephosphine ligand. Experimental and density functional theory calculation investigations support that the stereospecific rearrangement is based on the reversible formation of the kinetically favored cis-disubstituted spirocyclopropane intermediate.

Rhodium-Catalyzed Tandem Asymmetric Allylic Decarboxylative Addition and Cyclization of Vinylethylene Carbonates with N-Nosylimines

“…Since Hayashi [ 6 ] reported the first Rh-catalyzed asymmetric allylic alkylation employing a bidentate N , P -ligand in 2003, a variety of bidentate ligands has been discovered or designed to succeed in the asymmetric allylic substitution reaction [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. Recently, Li [ 15 , 16 , 17 , 18 , 19 ] developed a Rh/ N , P , N -tridentate ligand [ 20 ] catalysis system, which has proven to be a powerful tool for catalyzing asymmetric allylic alkylation (AAA) reaction. A broad spectrum of nucleophiles including C, N, O, S, and even P [ 21 ] are compatible, showing a vigorousness of the tridentate ligand for allylic reaction ( Scheme 1 a).…”

Rhodium-Catalyzed Tandem Asymmetric Allylic Decarboxylative Addition and Cyclization of Vinylethylene Carbonates with N-nosylimines

“…Since Hayashi [6] reported the first Rh-catalyzed asymmetric allylic alkylation employing a bidentate N,P-ligand in 2003, a variety of bidentate ligands has been discovered or designed to succeed in the asymmetric allylic substitution reaction [7][8][9][10][11][12][13][14]. Recently, Li [15][16][17][18][19] developed a Rh/N,P,N-tridentate ligand [20] catalysis system, which has proven to be a powerful tool for catalyzing asymmetric allylic alkylation (AAA) reaction. A broad spectrum of nucleophiles including C, N, O, S, and even P [21] are compatible, showing a vigorousness of the tridentate ligand for allylic reaction (Scheme 1a).…”