Catalytic enantioselective reductive alkynylation of amides enables one-pot syntheses of pyrrolidine, piperidine and indolizidine alkaloids

Stereodivergent synthesis of 2-oxo-oligopyrrolidines by an iterative coupling strategy

Natural linear polyamines play diverse roles in physiological processes by interacting with receptors at the cellular level. Herein, we describe the stereodivergent synthesis of oligopyrrolidines, which are conformationally constrained polyamines. We synthesized dimeric and trimeric 2-oxo-oligopyrrolidines using an iterative coupling strategy. The key to our success is an iridium-catalyzed trans/cis-selective nucleophilic addition and subsequent threo/erythro-stereoselective reduction. The synthesized pyrrolidines show varying cytotoxicities against a human cancer cell line depending on the number of rings and their stereochemistry.

Asymmetric Deoxygenative Functionalization of Secondary Amides with Vinylpyridines Enabled by a Triple Iridium-Photoredox-Chiral Phosphoric Acid System

An enantioselective deoxygenative functionalization of secondary amides with vinylpridines is developed by merging relay iridium catalysis and cooperative photoredox-chiral Brønsted acid catalysis, affording a series of valuable chiral amines in moderate to good yields with good enantioselectivities. The intriguing multiple catalytic system invoking triple-catalysis was found to be the key to the success of the current reactions, which may stimulate further development of catalytic methodologies for asymmetric deoxygenative transformations of amides.

Deoxygenative Nucleophilic Phosphonation and Electrophilic Alkylation of Secondary Amides: A Facile Access to Quaternary α-Aminophosphonates

The widespread occurrence and synthetic accessibility of amides render them valuable precursors for the synthesis of diverse nitrogen-containing compounds. Herein, we present a metal-free and streamlined synthetic strategy for the synthesis of quaternary α-aminophosphonates. This approach involves sequential deoxygenative nucleophilic phosphonation and versatile electrophilic alkylation of secondary amides in a one-pot fashion. Notably, this method enables the direct bis-functionalization of secondary amides with both nucleophiles and electrophiles for the first time, with simple derivatization leading to valuable free α-aminophosphonates by hydrolysis. The protocol has the advantages of operational simplicity, broad functional-group compatibility, environmental friendliness, and scalability to multigram quantities.

Iridium-Catalyzed Reductive (3+2) Annulation of Lactams Enabling the Rapid Total Synthesis of (±)-Eburnamonine

A reductive (3+2) annulation of lactams through iridium-catalyzed hydrosilylation and photoredox coupling with α-bromoacetic acid was developed. The iridium-catalyzed hydrosilylation of the lactam carbonyl group and subsequent elimination provide a transient cyclic enamine, which undergoes iridium-catalyzed photoredox coupling with α-bromoacetic acid in a one-pot process. The developed conditions show high functional-group tolerance and provide cyclic N,O-acetals containing a quaternary carbon center. The resulting N,O-acetals undergo a variety of acid-mediated nucleophilic addition reactions via iminium ions to give substituted cyclic amines. The developed sequence including reductive (3+2) annulation and acid-mediated nucleophilic addition was successfully applied to the four-step total synthesis of (±)-eburnamonine.

Chemoselective α-Trifluoroacetylation of Amides Using Highly Electrophilic Trifluoroacetic Anhydrides and 2,4,6-Collidine

Chemoselective α-acylation of tertiary amides proceeded with highly electrophilic acid anhydrides and weak bases under mild conditions. β-Ketoamides containing trifluoroacetyl or perfluoroacyl groups were selectively obtained even in the presence of other functional groups such as ketone, ester, etc. Density functional theory calculations suggest that 1-acyloxyenamine is the key intermediate for the chemoselective α-acylation.