Subhabrata Sen

We report a catalyst‐, acid‐, and base‐free strategy for activation of an N–N‐containing diaziridine/diazo‐derived framework enabling the synthesis of unsymmetrical azobenzenes via a mechanochemical three‐component reaction in a horizontal bead mill (DYNO‐MILL). The process proceeds through in situ formation of a diaziridine intermediate from a formal 2 + 1 annulation of diazo esters and dialkyl azodicarboxylates, followed by electrophile‐induced N─N bond reorganization with aryl diazonium tetrafluoroborates. This solvent‐minimized, operationally simple protocol tolerates air and moisture and is scalable. The resulting azobenzenes serve as versatile substrates for oxidant‐free electrochemical conversion to substituted tetrazoles without chromatographic purification. Green metrics analysis for the tetrazole formation reveals a significant improvement in atom economy (77.33%) compared to literature methods (29.98%–34.96%) and an enhanced Eco‐Scale score (73), highlighting the sustainability of this approach.

The development of ferroelectric materials is fundamentally constrained by the stringent requirement for crystallization within polar space groups. Moreover, integrating multiple functionalities, such as ferroelectricity, piezoelectricity, and negative thermal expansion (NTE), into a single‐component organic material remains a significant challenge, despite the demand for sustainable, wearable, high‐precision electronics. In this study, we report a symmetry‐breaking strategy to transform para‐halogenated 3‐oxo‐2‐phenylhydrazineyline indolines from centrosymmetric to polar space groups via controlled oxidation. The novel isostructural oxo‐derivatives exhibit robust ferroelectricity ( P _s and E _c ranging from 1.3 to 6.3 µC .cm ⁻² and 4 to 9.6 kV.cm ⁻¹ , respectively), supported by quantum‐mechanical calculations. Detailed crystal structure analysis reveals the mechanisms governing their polarization and ferroelectric domain switching. Leveraging its superior polarization, the chloro‐analog‐based device demonstrated high‐performance memristive behavior with stable bipolar resistive switching at minimal bias (∼1 V). The piezoelectric nanogenerators demonstrated superior energy‐harvesting capabilities, including rapid charging and high power density (up to 4.23 µW.cm ⁻² ). Additionally, bromo‐ and iodo‐analogs experienced moderate to colossal axial NTE, and all three analogs displayed minimal volumetric expansion. This study represents the first demonstration of single‐component organic materials that unite ferroelectric, piezoelectric, and NTE properties, providing a blueprint for multifunctional, high‐precision micro‐ and nanoelectronics.

We report a sustainable DYNO‐MILL‐assisted mechanochemical synthesis of pyrrolo[3,4‐ c ]pyrazoles via (3 + 2) cycloaddition between in situ generated nitrile imines and maleimides. Design of experiments (DoE) optimization identified key milling parameters, enabling efficient product formation in up to 78% yield under solvent‐minimized, catalyst‐free conditions. The method provides broad substrate scope, operational simplicity, and scalability. Comparative green metrics analysis highlights reduced waste generation and improved sustainability relative to conventional solution‐phase approaches.

We report a sustainable strategy for the direct C–H functionalization of pyridines, quinolines, isoquinolines, quinoxalines, pyrimidine, and pyrazine to access N‐aryl‐7‐azaindazoles and related fused azaheterocycles. N‐Heteroarene ylides, generated from readily available corresponding precursors, react with aryl diazonium tetrafluoroborates in the presence of DABCO through an ionic cascade of nucleophilic substitution, intramolecular S _N Ar, electrocyclization, and rearomatization. Deep eutectic solvents (DES) serve as efficient and green media, stabilizing diazonium salts, mitigating safety concerns, and enabling these transformations under mild conditions at 60°C with broad substrate scope. This protocol establishes DES as a safe and environmentally benign platform for heteroarene editing and late‐stage diversification of drug‐like molecules. Downstream functionalization of the final azaindazoles was demonstrated. Some of the final compounds demonstrated moderate antibacterial activity against antibiotic‐resistant gram‐ve bacteria.

The development of sustainable methods for controlled C–N bond formation remains a central challenge in modern synthesis.

We report a dual electrochemical-photochemical platform that enables selective hydroalkylation of N-aryl maleimides for the construction of C4-functionalized N-aryl succinimides in the presence of alcohol (as a solvent) and aryl diazo esters. Alternate electrode electrolysis (AEE) selectively promotes electrochemical reduction of N-aryl maleimides which undergoes cyclopropanation with a carbene (generated by blue LED irradiation of diazo esters), subsequent ketyl radical-mediated ring opening, and electro-oxidative nucleophilic attack by alcohol afford the densely substituted hydroalkylated succinimide derivative. No cross-reactivity or degradation of intermediates was observed. The protocol showcases high functional group tolerance, affording over 26 structurally diverse N-aryl succinimide derivatives, including the late-stage functionalization of aromatic amine-containing pharmaceutical scaffolds. A gram-scale synthesis underscores the scalability and operational simplicity of the process. Control experiments highlight the orthogonal yet complementary nature of the activation modes and provide mechanistic evidence supporting a stepwise paired electrolysis process aided with photochemical carbene generation pathway.

The synthesis of the potential indoleamine-2, 3-dioxygenase 1 (IDO1) degrader proteolysis-targeting chimeras (PROTAC) using sustainable reagents and technologies such as ionic liquids and photochemical couplings was investigated. The ligand to the protein of interest, an indole derivative, was synthesized successfully for three substrates bearing different substituents (NO2, (CF3)2 and H) over three steps with good to satisfactory results with overall yields ranging from 21 to 71%. However, the coupling with the ubiquitin ligase, pomalidomide, was unsuccessful due to the degradation of the reactive diazoketone functional group.