Dynamic Covalent Bond-Based Polymer Chains Operating Reversibly with Temperature Changes

Dynamic bonds can facilitate reversible formation and dissociation of connections in response to external stimuli, endowing materials with shape memory and self-healing capabilities. Temperature is an external stimulus that can be easily controlled through heat. Dynamic covalent bonds in response to temperature can reversibly connect, exchange, and convert chains in the polymer. In this review, we introduce dynamic covalent bonds that operate without catalysts in various temperature ranges. The basic bonding mechanism and the kinetics are examined to understand dynamic covalent chemistry reversibly performed by equilibrium control. Furthermore, a recent synthesis method that implements dynamic covalent coupling based on various polymers is introduced. Dynamic covalent bonds that operate depending on temperature can be applied and expand the use of polymers, providing predictions for the development of future smart materials.

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.

Novel Convenient Approach to 6-, 7-, and 8-Numbered Nitrogen Heterocycles Incorporating Endocyclic Sulfonamide Fragment

A new effective method for the construction of nitrogen heterocycles incorporating endocyclic pharmacophore sulfonamide fragment, based on the use of easy accessible N-(chlorosulfonyl)imidoyl chloride, CCl₃C(Cl)=NSO₂Cl (1), has been developed. Thus, a reaction of 1 as bielectrophilic 1,3-C–N–S reagent with benzylamines that act as 1,4-N–C–C-C binucleophiles, affords respective 1,2,4-benzothiadiazepine-1,1-dioxides. On the other hand, 1 reacts with alkenyl amines with the formation of respective N-alkenyl amidines undergoing Lewis acids initiated intramolecular cyclization to afford derivatives of 1,2,4-thiadiazines and 1,2,4-thiadiazocines bearing a halomethyl group able for further functionalization. The first examples of electrophilic heterocyclization of the chlorosulfonyl group onto an alkenyl or alkynyl group have been revealed.

Ruthenium(ii)-catalyzed intermolecular annulation of alkenyl sulfonamides with alkynes: access to bicyclic sultams

A ruthenium-catalyzed allylic C(sp3)-H activation strategy has been employed to develop an intermolecular coupling of alkenyl sulfonamides with alkynes. This protocol features the diastereoselective construction of [3.3.0] and [4.3.0] bicyclic sultams in one step.

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.

Selective synthesis of three product classes from imine and carboxylic acid precursors via direct imine acylation

Three divergent procedures allow the selective generation of δ-lactams, β-lactams and tetrahydropyrimidinones from common imine and carboxylic acid precursors.