The highly enantioselective Michael addition of ketones to nitrodienes catalyzed by the efficient organocatalyst system of pyrrolidinyl-thioimidazole and chiral thioureido acid
The highlyenantioselectiveMichaeladdition reaction of ketones to nitrodienes was promoted efficiently by the accessible and fine-tunable organocatalytic system of pyrrolidinyl-thioimidazole and chiral thioureido acid. The corresponding adducts were afforded in good yields with high diastereoselectivities (up to 99 : 1) and excellent enantioselectivities (up to 99% ee).
The asymmetric organocatalyzed Michael addition of aldehydes to alpha,beta-gamma,delta-unsaturated nitro compounds has been accomplished using only 5 mol % of (S)-diphenylprolinol silyl ether and 2 equiv of aldehyde in a mixture of ethanol and water (5% v/v). The Michael adducts were obtained in good yields, diastereoselectivities up to 94/6, and ee's up to 99%. This process provides synthetically useful compounds which can easily lead to more complex molecules, as exemplified with substituted tetrahydropyran or cyclohexene.
Organocatalyzed Conjugate Addition of Carbonyl Compounds to Nitrodienes/Nitroenynes and Synthetic Applications
The purpose of this study is to point out the synthetic utility of a new class of Michael acceptors (nitrodienes and nitroenynes). The highly enantioselective organocatalytic Michael addition of carbonylcompounds to these functionalized nitroolefins has been carried out in the presence of (S)‐diphenylprolinol silyl ether to achieve some interesting building blocks in high selectivities. The adducts