Brønsted Acid Catalyzed Enantioselective 1,3-Dipolar Cycloaddition

Significance

An asymmetric 1,3-dipolar cyclo­addition of nitrones with ethyl vinyl ether catalyzed by chiral phosphoramides is reported. The presented reaction yields the endo products as the major diastereomer. Several phosphoramides bearing different aryl groups at the 3,3′-positions of the binol backbone were screened, with catalyst 1 giving the best results. A variety of diaryl nitrones could be employed in this reaction. High enantioselectivities were obtained only with electron-deficient aryl groups.