Substituent-Controlled Annuloselectivity and Stereoselectivity in the Sulfa-Staudinger Cycloadditions

Aryne and CO2-based formal [2 + 2 + 2] annulation to access tetrahydroisoquinoline-fused benzoxazinones

Tetrahydroisoquinoline and its fused polyheterocycles are prevalent structural motifs found in numerous natural products. In this study, we report a highly efficient and convergent synthetic approach for the construction of tetrahydroisoquinoline-fused polyheterocycles through a three-component formal [2 + 2 + 2] annulation process by combining 3,4-dihydroisoquinolines, CO2, and benzynes. Notably, electron-rich 3,4-dihydroisoquinolines and electron-deficient benzynes exhibit greater reactivity in this annulation. Moreover, this method benefits from the convergent synthesis and the utilization of carbon dioxide, providing a valuable strategy for the facile synthesis of tetrahydroisoquinoline-fused polyheterocycles, with potential applications in the discovery and development of novel organic molecules.

Direct synthesis of highly strained bifunctionalized 2H-thiete 1,1-dioxides

Various bifunctionalized dialkyl 2H-thiete-2,3-dicarboxylate 1,1-dioxides are directly and convergently synthesized from readily available sulfonyl chlorides and dialkyl acetylenedicarboxylates via the pyridine-mediated [2 + 2] annulation.

Synthesis and anti-parasitic activity of N-benzylated phosphoramidate Mg2+-chelating ligands

A series of N-benzylated phosphoramidate esters, containing a 3,4-dihydroxyphenyl Mg²⁺-chelating group, has been synthesised in five steps as analogues of fosmidomycin, a Plasmodium falciparum 1-deoxy-1-d-xylulose-5-phosphate reductoisomerase (PfDXR) inhibitor. The 3,4-dihydroxyphenyl group effectively replaces the Mg²⁺-chelating hydroxamic acid group in fosmidomycin. The compounds showed very encouraging anti-parasitic activity with IC₅₀ values of 5.6-16.4 µM against Plasmodium falciparum parasites and IC₅₀ values of 5.2 - 10.2 µM against Trypanosoma brucei brucei (T.b.brucei). Data obtained from in silico docking of the ligands in the PfDXR receptor cavity (3AU9)⁵ support their potential as PfDXR inhibitors.

Does the Reaction of Cyclopropyl Acid Chlorides and Imines To Form 1,3-Oxazin-4-enone Heterocycles Proceed via a Ketene or an N-Acyl-iminium Mechanism?

The mechanism of the reaction between cyclopropyl acid chlorides and imines to form 1,3-oxazin-4-enones was probed through physical and computational experiments. The data gathered strongly support the reaction proceeding through an N-acyl iminium intermediate mechanism rather than a ketene intermediate mechanism.

Synthesis of novel 1,2,4-thiadiazinane 1,1-dioxides via three component SuFEx type reaction

Herein, we report the preparation of 1,2,4-thiadiazinane 1,1-dioxides from reaction of β-aminoethane sulfonamides with dichloromethane, dibromomethane and formaldehyde as methylene donors.

Ortho-Nitro Effect on the Diastereoselective Control in Sulfa-Staudinger and Staudinger Cycloadditions

The ortho-nitro effect was discovered in sulfa-Staudinger cycloadditions of ethoxycarbonylsulfene with linear imines. When an ortho-nitro group is present at the C-aryl substituents of linear imines, the sulfa-Staudinger cycloadditions deliver cis-β-sultams in considerable amounts, together with the predominant trans-β-sultams. In other cases, the above sulfa-Staudinger cycloadditions give rise to trans-β-sultams exclusively. Further mechanistic rationalization discloses that the ortho-nitro effect is attributed to its strong electron-withdrawing inductive effect. Similarly, the ortho-nitro effect also exists in Staudinger cycloadditions of ethoxycarbonyl ketene with the imines. The current research provides further insights into the diastereoselective control in sulfa-Staudinger and Staudinger cycloadditions.

Sterically controlled diastereoselectivity in thio-Staudinger cycloadditions of alkyl/alkenyl/aryl-substituted thioketenes

Diastereoselectivity in [2 + 2] cycloadditions of alkyl/alkenyl/arylthioketenes and imines, named as thio-Staudinger cycloaddition, was rationalized and verified.

Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

The mechanism and stereochemistry of [2^t + 2ⁱ + 2ⁱ] annulations between one thioketene molecule and two imine molecules have been studied experimentally and theoretically.

Construction of 2,3,4,5-tetrahydro-1,2,4-triazines via [4 + 2] cycloaddition of α-halogeno hydrazones to imines

In the presence of sodium carbonate, the [4 + 2] cycloaddition of α-halogeno hydrazones to imines proceeded readily, and furnished 2,3,4,5-tetrahydro-1,2,4-triazines in moderate to high chemical yields.

Synthesis of 2-oxophosphorindolines via the copper-catalyzed intramolecular aromatic C–H insertion of diazophosphonamidates

2-Ethoxy-2-oxophosphorindolines, benzo-γ-phospholactams, were synthesized efficiently with up to 97% yield through the copper-catalyzed intramolecular aromatic C–H insertion of diazophosphonamidates.

A telescopic one-pot synthesis of β-lactam rings using amines as a convenient source of imines

A facile synthetic approach to substituted β-lactams was designed, using secondary benzylic amines and acid chlorides as starting materials. The reactions proceeded smoothly and all the products were obtained in good yields.

Temperature-dependent annuloselectivity and stereochemistry in the reactions of methanesulfonyl sulfene with imines

The annuloselectivity in the reactions of methanesulfonyl sulfene and imines varies with temperature. At 20 °C, the [2^s+ 2ⁱ] annulation occurs exclusively, while at −78 °C, the [2^s+ 2ⁱ+ 2ⁱ] annulation ofN-methyl imines takes place specifically.

Annuloselectivity and stereochemistry in the sulfa-Staudinger cycloadditions of cyclic imines

The annuloselectivity and the stereochemistry in the [2^s+ 2ⁱ+ 2ⁱ] annulations in the sulfa-Staudinger cycloadditions of cyclic imines are controlled by the steric hindrance of cyclic imines. A stepwise [4 + 2] annulation mechanism is proposed.