Chiral Aldehyde–Palladium Catalysis Enables Asymmetric Synthesis of α‑Alkyl Tryptophans via Cascade Heck-Alkylation Reaction

The first catalytic asymmetric cascade Heck-alkylation reaction of NH2-unprotected amino acid esters with N-(2-iodophenyl)allenamides is reported in this work. Under the promotion of a combining catalytic system comprising a chiral aldehyde, a chiral palladium complex, and the Lewis acid ZnCl2, the title reaction takes place smoothly, giving optically active α-alkyl tryptophan derivatives in moderate to good yields and excellent enantioselectivities. The target products can be converted into other structurally complex chiral indoles without the loss of enantioselectivities

Combining Chiral Aldehyde Catalysis and Transition-Metal Catalysis for Enantioselective α‑Allylic Alkylation of Amino Acid Esters

A chiral aldehyde is rationally combined with a Lewis acid and a transition metal for the first time to form a triple catalytic system. This cocatalytic system exhibits good catalytic activation and stereoselective-control abilities in the asymmetric α-allylation reaction of N-unprotected amino acid esters and allyl acetates. Optically active α,α-disubstituted α-amino acids (α-AAs) are generated in good yields (up to 87%) and enantioselectivities (up to 96% ee). Preliminary mechanism investigation indicates that the chiral aldehyde 3f acts both as an organocatalyst to activate the amino acid ester via the formation of a Schiff base, and as a ligand to facilitate the nucleophilic attack process by coordinating with π-allyl Pd­(II) species

Procedure for the Synthesis of Polysubstituted Carbazoles from 3‑Vinyl Indoles

A simple Brønsted acid catalyzed tandem reaction, including intermolecular nucleophilic addition, substitution and intramolecular cyclization, in a one-pot manner is described. Thirty two 2-indolyl substituted carbazoles are generated in good to excellent yields. Based on this tandem reaction strategy, the poly­(1,4-carbazole) is prepared for the first time. Preliminary studies indicate that the poly­(1,4-carbazole) has good thermostability and optical properties

Chiral Brønsted Acid-Catalyzed Direct Asymmetric Mannich Reaction

A chiral Brønsted acid-catalyzed direct asymmetric Mannich reaction has been described. Various phosphoric acids, prepared from BINOL and H8-BINOL derivatives, have been evaluated for catalyzing the direct Mannich reaction. In the presence of a truly catalytic amount of the phosphoric acid, anti-selective Mannich reactions of cyclic ketones with a wide scope of aldimines were obtained in high yields with excellent enantioselectivities (up to 98% ee) and high diastereomeric ratios (up to 98/2 dr). A one-pot Mannich reaction using aromatic ketones as donors proceeded smoothly to give β-amino carbonyls with fairly good enantioselectivities

Chiral Brønsted Acid-Catalyzed Direct Asymmetric Mannich Reaction

A chiral Brønsted acid-catalyzed direct asymmetric Mannich reaction has been described. Various phosphoric acids, prepared from BINOL and H8-BINOL derivatives, have been evaluated for catalyzing the direct Mannich reaction. In the presence of a truly catalytic amount of the phosphoric acid, anti-selective Mannich reactions of cyclic ketones with a wide scope of aldimines were obtained in high yields with excellent enantioselectivities (up to 98% ee) and high diastereomeric ratios (up to 98/2 dr). A one-pot Mannich reaction using aromatic ketones as donors proceeded smoothly to give β-amino carbonyls with fairly good enantioselectivities

The Direct Asymmetric Alkylation of α‑Amino Aldehydes with 3‑Indolylmethanols by Enamine Catalysis

This work describes an efficient α-alkylation reaction of α-amino aldehydes with 3-indolylmethanols. In the promotion of catalyst <b>3f</b>, the target products were obtained in high yields (up to 99%), good diastereoselectivities (up to 88:12), and excellent enantioselectivities (up to 96% ee). The direct alkylation products can be readily converted into other tryptophan derivatives without the loss of stereoselectivities

Chiral Brønsted Acid-Catalyzed Direct Asymmetric Mannich Reaction

A chiral Brønsted acid-catalyzed direct asymmetric Mannich reaction has been described. Various phosphoric acids, prepared from BINOL and H8-BINOL derivatives, have been evaluated for catalyzing the direct Mannich reaction. In the presence of a truly catalytic amount of the phosphoric acid, anti-selective Mannich reactions of cyclic ketones with a wide scope of aldimines were obtained in high yields with excellent enantioselectivities (up to 98% ee) and high diastereomeric ratios (up to 98/2 dr). A one-pot Mannich reaction using aromatic ketones as donors proceeded smoothly to give β-amino carbonyls with fairly good enantioselectivities

Asymmetric Synthesis of α‑Amino Ketones by Brønsted Acid Catalysis

The highly efficient, regioselective, and enantioselective transfer hydrogenation of α-keto ketimines and reductive amination of diketones by Brønsted acid catalysis is described. A series of chiral α-amino ketones is prepared in high yields (up to >99%), excellent regioselectivities (up to >99:1), and enantioselectivities (up to 98% ee). This method has broad substrate scope

Highly Enantioselective Alkylation Reaction of Enamides by Brønsted-Acid Catalysis

The H8−BINOL-derived, phosphoric acid catalyzed, highly enatioselective alkylation reaction of enamides with indolyl alcohols has been described. A phosphoric acid derived from H8-BINOL enabled an asymmetric α-alkylation of enamides with indolyl alcohols to give β-aryl 3-(3-indolyl)propanones in high yields (up to 96%) and with excellent enantioselectivity (up to 96% ee)

Core Structure-Oriented Asymmetric α‑Allenylic Alkylation of Amino Acid Esters Enabled by Chiral Aldehyde/Palladium Catalysis

Aiming at the reported chiral synthons leading to manzacidins A and D, here we report a highly efficient catalytic asymmetric α-allenylic alkylation reaction of NH2-unprotected amino acid esters that is promoted by combined chiral aldehyde/palladium catalysis. Fifty examples of unnatural α,α-disubstituted amino acid esters are reported with good-to-excellent yields and stereoselectivities. Based on this methodology, a key intermediate leading to manzacidin C and its other three stereoisomers is prepared accordingly