4 research outputs found
Rhodium-Catalyzed Hydroboration: Directed Asymmetric Desymmetrization
Rhodium-catalyzed asymmetric hydroboration in conjunction with directing groups can be used control relative and absolute stereochemistry. Hydroboration has the potential to create new CāC, CāO, and CāN bonds from an intermediate CāB bond with retention of stereochemistry. Desymmetrization resulting in the loss of one or more symmetry elements can give rise to molecular chirality, i.e., the conversion of a prochiral molecule to one that is chiral. Unsaturated amides and esters hold the potential for two-point binding to the rhodium catalyst and have been shown to direct the regiochemistry and impact stereochemistry in asymmetric hydroborations of acyclic Ī²,Ī³-unsaturated substrates. In the present study, the pendant amide functionality directs the hydroboration cis in the cyclic substrates studied; the corresponding ester substrates do so to a lesser extent. The enantioselectivity is determined by regioselective addition to the re or si site of the rhodium-complexed alkene. The effect of catalyst, ligand and borane on the observed diastereoselectivity and enantioselectivity for a variety of cyclopentenyl ester and amide substrates is discussed
Enantioselective Desymmetrization via Carbonyl-Directed Catalytic Asymmetric Hydroboration and SuzukiāMiyaura Cross-Coupling
The rhodium-catalyzed enantioselective
desymmetrization of symmetric
Ī³,Ī“-unsaturated amides via carbonyl-directed catalytic
asymmetric hydroboration (directed CAHB) affords chiral secondary
organoboronates with up to 98% ee. The chiral Ī³-borylated products
undergo palladium-catalyzed SuzukiāMiyaura cross-coupling via
the trifluoroborate salt with stereoretention
Enantioselective Desymmetrization via Carbonyl-Directed Catalytic Asymmetric Hydroboration and SuzukiāMiyaura Cross-Coupling
The rhodium-catalyzed enantioselective
desymmetrization of symmetric
Ī³,Ī“-unsaturated amides via carbonyl-directed catalytic
asymmetric hydroboration (directed CAHB) affords chiral secondary
organoboronates with up to 98% ee. The chiral Ī³-borylated products
undergo palladium-catalyzed SuzukiāMiyaura cross-coupling via
the trifluoroborate salt with stereoretention