Design of chiral indium complexes for enantioselective carbon-carbon bond formation reactions

Abstract

A novel chiral indium complex generated from indium(III) chloride and (S)-1,1-Bi-2-napthol (BINOL) has been discovered to effect high enantioselectivities in the catalytic enantioselective addition of allyltributylstannanes to aldehydes. The synthesis of optically pure secondary homoallylic alcohols was also accomplished by the reaction of aldehydes with allyltributylstannanes catalyzed by another novel chiral indium(III) complex prepared from (S,S)-PYBOX ligand and In(OTf)3. The allylation protocols resulted in good yields and high enantioselectivities (96% ee).The BINOL-In(III) and (S,S)-PYBOX-In(III) chiral indium complexes has been discovered to acts as efficent chiral Lewis acid catalyst for the enantioselective allylation of ketones. The tertiary alcohols were isolated in good yields and moderate to high enantioselectivities (up to 92% ee) in both systems.The successful application of the chiral (S)-BINOL-In(III) complex to enantioselective Diels-Alder reaction was accomplished. The cycloaddition of cyclic and open-chained dienes to 2-methacrolein and 2-bromoacrolein resulted in good yields and excellent enantioselectivities (98% ee).