Enantioselective Additions of Aryltitanium Tris(isopropoxide) to Ketones: Structure of [(i-PrO)2Ti{μ-(S)-BINOLate}(μ-O-i-Pr)TiPh(O-i-Pr)2], Study of Mechanistic and Stereochemical Insights

Enantioselective rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones: synthesis of α-hydroxy acids

The enantioselective addition of arylboronic acids to N-heteroaryl ketones provides a convenient access to chiral α-heteroaryl tertiary alcohols, yet addition reactions of this type have been challenging due to catalyst deactivation. In this report, an efficient rhodium-catalyzed addition of arylboronic acids to N-heteroaryl ketones is established, affording a variety of valuable α-heteroaryl alcohols with excellent functional group compatibility. The employment of the WingPhos ligand containing two anthryl groups is crucial for this transformation. In particular, a range of chiral benzoxazolyl-substituted tertiary alcohols were formed with excellent ee values and yields by employing a Rh loading as low as 0.3 mol%, which can serve as a practical protocol to furnish a series of chiral α-hydroxy acids after hydrolysis.

Manganese-Catalyzed Achmatowicz Rearrangement Using Green Oxidant H2O2

Oxidation reactions have been extensively studied in the context of the transformations of biomass-derived furans. However, in contrast to the vast literature on utilizing the stoichiometric oxidants, such as m-CPBA and NBS, catalytic methods for the oxidative furan-recyclizations remain scarcely investigated. Given this, we report a means of manganese-catalyzed oxidations of furan with low loading, achieving the Achmatowicz rearrangement in the presence of hydrogen peroxide as an environmentally benign oxidant under mild conditions with wide functional group compatibility.

Harnessing the Power of the Asymmetric Grignard Synthesis of Tertiary Alcohols: Ligand Development and Improved Scope Exemplified by One-Step Gossonorol Synthesis

A series of N-substituted cyclohexyldiaminophenolic ligands for the asymmetric Grignard synthesis of tertiary alcohols is reported. The 2,5-dimethylpyrrole-decorated ligand led to improved enantioselectivities and broadened the scope of the methodology. As an exemplar, we report an unprecedented highly selective one-step synthesis of gossonorol in 93% ee, also constituting the shortest formal syntheses of natural products boivinianin B and yingzhaosu C.

Enantioselective synthesis of gem-diarylalkanes by transition metal-catalyzed asymmetric arylations (TMCAAr)

To date, enantiomerically enriched molecules containing gem(1,1)-diaryl containing tertiary or quaternary stereogenic centers have been readily accessed by transition metal-catalyzed enantioselective or stereoconvergent aryl transfer reactions.

Chiral gem(1,1)-diaryl containing tertiary or quaternary stereogenic centers are present in many natural products and important pharmacophores. While numerous catalytic asymmetric methods enable access to 1,1-diaryl motifs, transition metal-catalyzed asymmetric arylations (TMCAAr) are one of the most powerful methods to prepare enantiopure gem-diarylalkane compounds. The main methodology includes enantioselective 1,2- or 1,4-additions across C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O, C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N and C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds by arylmetallic reagents; aryl cross-couplings of olefins, benzylic (pseudo)halides and aziridines; asymmetric aryl substitution reactions of allylic substrates; and isotopic benzylic C–H arylation.

Catalytic Enantioselective Arylation and Heteroarylation of Ketones with Organotitanium Reagents Generated In Situ

A practical and useful, catalytic enantioselective method has been developed for the synthesis of tertiary diaryl and aryl heteroaryl carbinols starting from commercially available aromatic ketones and aryl or heteroaryl bromides. In this method, organotitanium reagents are generated in situ from the bromides by lithiation with nBuLi followed by transmetallation of the resulting organolithiums with ClTi(OiPr)₃ . Treatment of the ketones with the titanium reagents in the presence of (R)-3-(3,5-bistrifluoromehthylphenyl)-1,1'-bi-2-naphthol (BTFP-BINOL) affords the corresponding tertiary alcohols in high enantioselectivities and yields. The reaction can also start with furan and 2-thienyllithium. The method is operationally simple and can be conducted on a 10-mmol scale without any difficulties.

Total Synthesis of (-)-Salvinorin A

Salvinorin A (1) is natural hallucinogen that binds the human κ-opioid receptor. A total synthesis has been developed that parlays the stereochemistry of l-(+)-tartaric acid into that of (-)-1 via an unprecedented allylic dithiane intramolecular Diels-Alder reaction to obtain the trans-decalin scaffold. Tsuji allylation set the C9 quaternary center and a late-stage stereoselective chiral ligand-assisted addition of a 3-titanium furan upon a C12 aldehyde/C17 methyl ester established the furanyl lactone moiety. The tartrate diol was finally converted into the C1,C2 keto-acetate.

Synthesis of β-acetoxy alcohols by PhI(OAc)2-mediated metal-free diastereoselective β-acetoxylation of alcohols

A PhI(OAc)₂-mediated metal-free β-acetoxylation method to synthesize diverse β-acetoxy alcohols has been achieved in good yields with high diastereoselectivity.

Asymmetric Addition of Pyridyl Aluminum Reagents to Aldehydes Catalyzed by a Titanium(IV) Catalytic System of (R)-H8-BINOLate

The asymmetric addition of pyridyl aluminum reagents to aldehydes has been successfully developed by employing a titanium(IV) catalytic system of (R)-H8-BINOLate, which affords a series of valuable optically active diarylmethanols containing various pyridyl groups in high yields with excellent enantioselectivities of up to 98% ee.

Enantioselective addition of ArTi(OiPr)3 to aldehydes catalyzed by a titanium complex of an N-sulfonylated amino alcohol

Asymmetric additions of ArTi(OⁱPr)₃ to aldehydes catalyzed by a titanium catalyst of N-sulfonylated amino alcohols to afford desired secondary alcohols in good yields with good to excellent enantioselectivities of up to 95% ee.

MgBr2-promoted enantioselective aryl addition of ArTi(OiPr)3 to ketones catalyzed by a titanium(iv) catalyst of N,N′-sulfonylated (1R,2R)-cyclohexane-1,2-diamine

MgBr₂-promoted asymmetric addition of ArTi(OⁱPr)₃ to ketones catalyzed by a titanium catalyst of N,N′-sulfonylated (1R,2R)-cyclohexane-1,2-diamines to afford desired tertiary alcohols in good to excellent enantioselectivities of up to 95% ee.