Nickel-Catalyzed Asymmetric Addition of Aromatic Halides to Ketones: Highly Enantioselective Synthesis of Chiral 2,3-Dihydrobenzofurans Containing a Tertiary Alcohol
A highlyenantioselective and straightforward synthetic procedure to chiral 3-hydroxy-2,3-dihydrobenzofurans has been developed by nickel/bisoxazoline-catalyzed intramolecular asymmetric addition of aryl halides to unactivated ketones, giving 2,3-dihydrobenzofurans with a chiral tertiary alcohol at the C-3 position in good yields and excellent enantioselectivities (up to 92% yield and 98% ee). The
Copper(I)-Catalyzed Intramolecular Caryl-O Bond-Forming Cyclization for the Synthesis of 1,4-Benzodioxines and Its Application in the Total Synthesis of Sweetening Isovanillins
作者:Govindasamy Sekar、Ajay Naidu、D. Ganapathy
DOI:10.1055/s-0030-1258206
日期:2010.10
Various substituted 1,4-benzodioxines were synthesized through an Ullmann-type intramolecular Caryl-O coupling cyclization reaction using a catalytic amount of BINOL-CuI complex. This methodology was successfully utilized as the key step in the total synthesis of isovanillyl sweetening agents 5-(2,3-dihydro-1,4-benzodioxin-2-yl)-2-methoxyphenol and 5-(2,3-dihydro-1,4-benzoxathiin-2-yl)-2-methoxyphenol in 15.8% and 14.85% overall yields in five steps from isovanillin.