Preparation and application of bisoxazoline ligands with a chiral spirobiindane skeleton for asymmetric cyclopropanation and allylic oxidation

A new type of bisoxazoline ligand 4 (abbreviated as SpiroBOX) containing a chiral spirobiindane scaffold were easily prepared in high yields from enantiomerically pure 1,1′-spirobiindane-7,7′-diol (SPINOL) with 1,1′-spirobiindane-7,7′-dicarboxylic acid as the key intermediate. Ligands 4 were applied to the Cu-catalyzed asymmetric cyclopropanation of styrenes with menthyl diazoacetate and allylic oxidation of cyclic alkenes with tert-butyl perbenzoates. The copper complexes of ligands 4 showed high activities and moderate to good enantioselectivities.

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(R)-7,7′-Bis(trifluoromethanesulfonyloxy)-1,1′-spirobiindaneC19H14F6O6S2Ee = 100%[α]D20=+143 (c 0.5, CH2Cl2)Source of chirality: resolutionAbsolute configuration: R

(R)-1,1′-Spirobiindane-7,7′-dicarbonitrileC19H14N2Ee = 100%[α]D20=+144 (c 0.5, CH2Cl2)Source of chirality: resolutionAbsolute configuration: R

(R)-1,1′-Spirobiindanyl-7,7′-dicarboxylic acidC19H16O4Ee = 100%[α]D20=+303 (c 0.5, CH2Cl2)Source of chirality: resolutionAbsolute configuration: R

(Ra,S,S)-N,N′-Bis(2-hydroxy-1-phenylethyl)-1,1′-spirobiindane-7,7′-diamideC35H34N2O4Ee = 100%[α]D20=+102 (c 0.5, CHCl3)Source of chirality: resolution and natural productsAbsolute configuration: R,S,S

(Sa,S,S)-N,N′-Bis(2-hydroxy-1-phenylethyl)-1,1′-spirobiindane-7,7′-diamideC35H34N2O4Ee = 100%[α]D20=-103 (c 0.5, CHCl3)Source of chirality: resolution and natural productsAbsolute configuration: R,S,S

(Ra,S,S)-N,N′-Bis(1-benzyl-2-hydroxyethyl)-1,1′-spirobiindane-7,7′-diamideC37H38N2O4Ee = 100%[α]D20=+90 (c 0.5, CHCl3)Source of chirality: resolution and natural productsAbsolute configuration: R,S,S

(Ra,S,S)-N,N′-Bis(1-hydroxymethyl-2-methylpropyl)-1,1′-spirobiindane-7,7′-diamideC29H38N2O4Ee = 100%[α]D20=+84 (c 0.5, CHCl3)Source of chirality: resolution and natural productsAbsolute configuration: R,S,S

(Ra,S,S)-7,7′-Bis(4-phenyloxazolin-2-yl)-1,1′-spirobiindaneC35H30N2O2Ee = 100%[α]D20=+93 (c 0.5, CH2Cl2)Source of chirality: resolution and natural productsAbsolute configuration: R,S,S

(Sa,S,S)-7,7′-Bis(4-phenyloxazolin-2-yl)-1,1′-spirobiindaneC35H30N2O2Ee = 100%[α]D20=-322 (c 0.5, CH2Cl2)Source of chirality: resolution and natural productsAbsolute configuration: S,S,S

(Ra,S,S)-7,7′-Bis(4-benzyloxazolin-2-yl)-1,1′-spirobiindaneC37H34N2O2Ee = 100%[α]D20=+111 (c 0.5, CH2Cl2)Source of chirality: resolution and nature productsAbsolute configuration: R,S,S

(Ra,S,S)-7,7′-Bis(4-isopropyloxazolin-2-yl)-1,1′-spirobiindaneC29H34N2O2Ee = 100%[α]D20=+155 (c 0.5, CH2Cl2)Source of chirality: resolution and nature productsAbsolute configuration: R,S,S