Highly Enantioselective Catalytic Benzoyloxylation of 3‐Aryloxindoles Using Chiral VAPOL Calcium Phosphate

Vaulted Biaryls in Catalysis: A Structure–Activity Relationship Guided Tour of the Immanent Domain of the VANOL Ligand

“…The vaulted biaryl ligands VANOL and VAPOL have been demonstrated to be effective in a variety of useful catalytic asymmetric reactions including amidation of imines,1 aminoallylation of aldehydes,2 aza‐Darzens reaction3 cis ‐aziridination of imines4, 5 trans ‐aziridination of imines,4q, 6 Baeyer–Villiger reactions,7 benzoyloxylation of aryloxindoles,8 desymmetrization of aziridines,9 Diels–Alder reactions,10 heteroatom Diels–Alder reactions,11 hydroarylation of alkenes,12 hydrogenation of alkenes,13 imidation of imines,14 Mannich reactions,15 multicomponent aziridination of aldehydes,16 Petasis reaction,17 propargylation of ketones,18 reduction of imines,19 chlorination and Michael reactions of oxindoles,20 hydroacylation of alkenes,21 pinacol rearrangement,22 reduction of aminals23 and Michael addition of alkynes 24…”

Chiral Ca-, Sr-, and Ba-Catalyzed Asymmetric Direct-Type Aldol, Michael, Mannich, and Related Reactions

“…From examination of the reactions using stoichiometric amounts of the chiral amide (CaL(HMDS)) and the substrate, it was assumed that the true active species was mostly on the homoleptic side, which means that these reactions were catalyzed by achiral Ca(HMDS) 2 not by chiral CaL(HMDS). Antilla et al reported chiral calcium-VAPOL phosphate-mediated asymmetric benzoyloxylations and chlorinations of 3-substituted oxindoles (Tables 28 and 29) [103]. It was shown that VAPOL phosphate could be applied to several reactions and that the desired products were obtained in excellent yields with high enantioselectivities.…”

Title Pages

“…Calcium salts have found novel applications, e.g. for formation of chiral 3-hydroxyoxindole derivatives using chiral VAPOL calcium phosphate 42 . Regarding frustrated ion pairs, a bisfluorenyl-substituted allene may now be used instead of tris(pentafluorophenyl)borane for their generation and utilized in cleavage of disulfides 43 , while chiral examples have found application in asymmetric hydrogenation of imines 44 .…”