Desymmetrization of meso-bisphosphates using copper catalysis and alkylzirconocene nucleophiles

The desymmetrization of meso-compounds is a useful synthetic method, as illustrated by numerous applications of this strategy in natural product synthesis. Cu-catalyzed allylic desymmetrizations enable the enantioselective formation of carbon-carbon bonds, but these transformations are limited in substrate scope and by the use of highly reactive premade organometallic reagents at cryogenic temperatures. Here we show that diverse meso-bisphosphates in combination with alkylzirconium nucleophiles undergo highly regio-, diastereo- and enantio-selective Cu-catalyzed desymmetrization reactions. In addition, C₂-symmetric chiral bisphosphates undergo stereospecific reactions and a racemic substrate undergoes a Cu-catalyzed kinetic resolution. The reaction tolerates functional groups incompatible with many common organometallic reagents and provides access to a broad range of functionalized carbo- and hetero-cyclic structures. The products bear up to three contiguous stereogenic centers, including quaternary centers and spirocyclic ring systems. We anticipate that the method will be a useful complement to existing catalytic enantioselective reactions.

Desymmetrization of meso-2,5-diallylpyrrolidinyl ureas through asymmetric palladium-catalyzed carboamination: stereocontrolled synthesis of bicyclic ureas

The stereoselective synthesis of fused bicyclic ureas 8 is accomplished via enantioselective Pd-catalyzed desymmetrizing carboamination reactions of meso -2,5-diallylpyrroldinyl urea 7c . The reactions generate a C–N bond, a C–C bond, and afford products bearing three stereocenters with good diastereoselectivity (6–12:1 dr) and enantioselectivity (up to 95:5 er). The N -(p -chlorophenyl) group can be cleaved in good yield using a two step sequence. In addition, 8c was transformed to a tricyclic guanidine product using a four-step (two pot) procedure and was converted to 9-epi -batzelladine k in seven steps.