Bis(μ-oxo)–Dititanium(IV)–Chiral Binaphthyldisulfonate Complexes for Highly Enantioselective Intramolecular Hydroalkoxylation of Nonactivated Alkenes

Abstract

A series of chiral 1,1′-binaphthyl-2,2′-disulfonic acids was designed, synthesized, and applied in a highly enantioselective Ti-catalyzed intramolecular hydroalkoxylation of nonactivated alkenes. The catalyst is probably a complex between two chiral binaphthyldisulfonate ligands and a bis(μ-oxo)−dititanium(IV) core structure. The sulfonamide groups of the ligands and water are necessary for the catalysis, as they may stabilize the catalytically active complex through hydrogen bonding. Various 2methylcoumarans were obtained in up to greater than 99% yields and up to 97% enantiomeric excess under mild conditions.

Catalytic Asymmetric Hydroalkoxylation of C–C Multiple Bonds

“…172 In 2021, Xie and Li reported a highly related intramolecular hydroalkoxylation using a chiral 1,1′-binaphthyl-2,2′-disulfonic acid (BINSA) in the presence of Ti(EHO) 4 (EHO = 2ethylhexyloxy) and water. 173 The shown intramolecular cyclizations of 2-allylphenols proceed under comparatively mild reaction conditions (75 °C) and generally improved enantioselectivities are observed, relative to the previous example. In line with Hintermann, the authors propose that such transformations proceed through a multinuclear titaniumμ-oxo species and have tentatively provided a possible mechanism, with the enantiodetermining step involving concomitant protonation of the alkene and C−O bond formation to yield enantioenriched cyclized products (Scheme 48).…”

“…In 2021, Xie and Li reported a highly related intramolecular hydroalkoxylation using a chiral 1,1′-binaphthyl-2,2′-disulfonic acid (BINSA) in the presence of Ti­(EHO) 4 (EHO = 2-ethylhexyloxy) and water . The shown intramolecular cyclizations of 2-allylphenols proceed under comparatively mild reaction conditions (75 °C) and generally improved enantioselectivities are observed, relative to the previous example.…”

Asymmetric Cationic Polymerization of Benzofuran through a Reversible Chain-Transfer Mechanism: Optically Active Polybenzofuran with Controlled Molecular Weights

“…In particular, the polymers obtained in toluene showed a very sharp peak at 49 ppm and a small distinctive peak at approximately 48 ppm. The peaks at 49 (X) and 48 ppm (Y) can be most probably ascribed to the trans-threo and cis-erythro enchainments of the BzF unit, respectively, according to the 13 C NMR spectra of trans- and cis-2,3-dihydoro-2,3-dimethyl benzofuran as model compounds and poly­(2,3-dihydrofuran) as similar cyclic vinyl ether polymers, where the peaks observed at a lower and higher magnetic filed were assigned to the trans- and cis-carbons, respectively. − The peak intensity ratio of X/Y was 95:5, indicating a high trans-threo selectivity during cationic polymerization with AlCl 3 and ( R )- 2a in toluene at −78 °C. This ratio was almost the same as that obtained without CTA1 (Figure S10).…”

Mechanistic Insight into Palladium/Brønsted Acid Catalyzed Methoxycarbonylation and Hydromethoxylation of Internal Alkene: A Computational Study

“…In this context, many characteristic transition-metal-catalyzed systems were designed to activate the alkene double bonds, leading to highly ingenious as well as useful reactions. Some famous examples, including the Wacker process, olefin metathesis, Heck reaction, alkoxycarbonylation, and hydroalkoxylation, have been extensively used in the preparation of complex organic molecules in industry production. Particularly, palladium-catalyzed alkoxycarbonylation and hydroalkoxylation reactions of alkenes provide a highly atom economic and more environmentally friendly method for ester and ether synthesis. , …”