Divergent syntheses of L-733, 060 and CP-122721 from functionalized pieridinones made by one-pot tandem cyclization

Harnessing the Reactivity of Nitroarene Radical Anions to Create Quinoline N-Oxides by Electrochemical Reductive Cyclization

Electrochemical reduction of 2-allyl-substituted nitroarenes using a simple, undivided electrochemical cell with non-precious electrodes to generate nitroarene radical anions was developed. The nitroarene radical anion intermediates participate in 1,5-hydrogen atom transfer reactions to construct quinoline N-oxides bearing aryl-, heteroaryl-, alkenyl-, benzyl-, sulfonyl-, or carboxyl groups.

Biocatalytic C-H oxidation meets radical cross-coupling: Simplifying complex piperidine synthesis

Modern medicinal chemists are targeting more complex molecules to address challenging biological targets, which leads to synthesizing structures with higher sp3 character (Fsp3) to enhance specificity as well as physiochemical properties. Although traditional flat, high-fraction sp2 molecules, such as pyridine, can be decorated through electrophilic aromatic substitution and palladium (Pd)-based cross-couplings, general strategies to derivatize three-dimensional (3D) saturated molecules are far less developed. In this work, we present an approach for the rapid, modular, enantiospecific, and diastereoselective functionalization of piperidine (saturated analog of pyridine), combining robust biocatalytic carbon-hydrogen oxidation with radical cross-coupling. This combination is directly analogous to electrophilic aromatic substitution followed by Pd-couplings for flat molecules, streamlining synthesis of 3D molecules. This study offers a generalizable strategy for accessing complex architectures, appealing to both medicinal and process chemists.

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

The synthesis of nitrogen-containing heterocycles, including natural alkaloids and other compounds presenting different types of biological activities have proved to be successful employing chiral sulfinyl imines derived from tert-butanesulfinamide. These imines are versatile chiral auxiliaries and have been extensively used as eletrophiles in a wide range of reactions. The electron-withdrawing sulfinyl group facilitates the nucleophilic addition of organometallic compounds to the iminic carbon with high diastereoisomeric excess and the free amines obtained after an easy removal of the tert-butanesulfinyl group can be transformed into enantioenriched nitrogen-containing heterocycles. The goal of this review is to the highlight enantioselective syntheses of heterocycles involving the use of chiral N-tert-butanesulfinyl imines as reaction intermediates, including the synthesis of several natural products. The synthesis of nitrogen-containing heterocycles in which the nitrogen atom is not provided by the chiral imine will not be considered in this review. The sections are organized according to the size of the heterocycles. The present work will comprehensively cover the most pertinent contributions to this research area from 2012 to 2020. We regret in advance that some contributions are excluded in order to maintain a concise format.

Shono-Type Oxidation for Functionalization of N-Heterocycles

The development of facile synthetic methods for stereodefined aliphatic cyclic amines is an important research field in synthetic organic chemistry since such scaffolds constitute a variety of natural products and biologically active compounds. N-Acyl cyclic N,O-acetals which prepared by electrochemical oxidation of the corresponding cyclic amines have proven to be useful and versatile precursors for the synthesis of such skeletons. In this Personal Account, we introduce our efforts toward the development of synthetic strategies for the diastereo- and/or enantioselective synthesis of cyclic amines by using electrochemically prepared cyclic N,O-acetals. In addition, the investigation of the "memory of chirality" in the electrooxidative methoxylation of N-acyl amino acid derivatives, the strategy for the synthesis of chiral azabicyclic compounds by utilizing electrochemical oxidation, and halogen cation-mediated synthesis of nitrogen-containing heterocycles are also described.

Chiral N-tert-Butylsulfinyl Imines: New Discoveries

In this account the reactions of chiral N-tert-butylsulfinyl imines with organometallic reagents such as organoalkaline (lithium, sodium, potassium and cesium derivatives), organomagnesium, organozinc, organoboron, organoaluminium, organoindium and organosilicon compounds is comprehensively described. The reactivity in all cases is derived to synthetic applications in order to prepare interesting organic nitrogenated molecules, especially in the field of alkaloid compounds.

A diastereoselective approach to amino alcohols and application for divergent synthesis of dolastatin 10

A diastereoselective approach to obtain amino alcohols through SmI₂-induced radical addition and divergent synthesis of dolastatin 10 are described.

Synthesis of 2-Arylpiperidines via Pd-Catalyzed Arylation of Aza-Achmatowicz Rearrangement Products with Arylboronic Acids

The first Pd-catalyzed arylation of aza-Achmatowicz rearrangement products with arylboronic acids is achieved, providing versatile 2-aryldihydropyridinones for facile synthesis of highly functionalized 2-arylpiperidines. Key to this arylation is the use of non-phosphine-ligand palladium precatalyst. The substrate scope is demonstrated with >26 examples, and the utility of 2-aryldihydropyridinones is illustrated by the synthesis of a small collection of 2-arylpiperidines with substituents or functional groups at any carbon (C2-C6) as well as two NK₁ receptor antagonists (+)-CP-999,94 and (+)-L-733,060.