Organocatalytic Asymmetric [2 + 4] Cycloadditions of 3-Vinylindoles with <i>ortho</i>-Quinone Methides

Abstract

Catalytic asymmetric [2 + 4] cycloadditions of 3-vinylindoles with ortho-quinone methides and their precursors were carried out in the presence of chiral phosphoric acid to afford a series of indole-containing chroman derivatives with structural diversity in overall high yields (up to 98%), good diastereoselectivities (up to 93:7 dr) and moderate to excellent enantioselectivities (up to 98% ee). This approach not only enriches the chemistry of catalytic asymmetric cycloadditions involving 3-vinylindoles but is also useful for synthesizing chiral chroman derivatives.

Keywords

• vinylindoles
• cycloaddition
• <i>ortho</i>-quinone methide
• chiral phosphoric acid
• asymmetric organocatalysis