Presence of cyclobutane rings in bioactive natural products makes them a popular synthetic target. Most common strategy for synthesizing cyclobutanes is [2+2] cycloaddition, which is usually facilitated by using ultraviolet radiation and catalysts. Herein we report the design and synthesis of densely functionalized cyclobutanes by alleviating these drawbacks and using sunlight. Further, we identified the putative mechanism of the transformation based on kinetic, fluorescence and crystallographic studies and evaluated biological activities of the products against MCF7 cell lines. The rational design of the olefinic substrates was based on their UV–vis spectra. The generic aspect of the reaction was elucidated by the syntheses of diverse analogs of cyclobutanes. Further, crystal structures and UV–vis spectra of the olefinic partners assisted us in rationalizing the stereoselectivity of the heterodimers. We believe this energy-efficient mild approach will provide a substantial contribution to the existing repertoire of strategies to regio- and stereoselectively access cyclobutanes. © 2018 Elsevier Ltd

Subhabrata Sen

Chemistry

(SoNS) School of Natural Sciences

Parthapratim Munshi

Kunal Kumar Jha

Sanjay Dutta

Saibal Sar

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Shiv Nadar University

Tetrahedron

A lightweight organic material, trans-4′-dimethylamino-4-nitro-α-cyanostilbene, exhibits notable charge carrier mobility (∼10 -4 cm 2 V -1 s -1 ). The non-centrosymmetric material also displays moderate second harmonic generation activity. This is one of the rarest examples of small organic materials displaying semiconductor characteristics. The charge-transfer pathway as elucidated via high-resolution single-crystal X-ray diffraction data based "energy frameworks" and "experimental charge density" analyses is assessed by measuring the charge carrier mobility using the space charge limited current technique on pure single-crystal diode devices. These advanced structural analyses clearly demonstrate that charge transport in organic crystals is purely governed by its molecular packing, especially the π-π stacking geometry. The balanced ambipolar charge transport behavior makes this highly soluble and thermally stable organic crystal promising for applications in optoelectronic devices. Moreover, this report introduces the crucial role of energy frameworks and charge density analyses for fundamental understanding of the structure-property relationship in organic semiconductors. Copyright © 2019 American Chemical Society.

Crystal Growth and Design

Structure-Property Relationship in an Organic Semiconductor: Insights from Energy Frameworks, Charge Density Analysis, and Diode Devices

Three isostructural polymorphs with two-dimensional and three-dimensional similarities are demonstrated quantitatively from similarity relationship analysis. The similarity dimensions are then visualized and correlated in a novel way via qualitative analysis using 'energy frameworks'. Two of the three polymorphs with three-dimensional similarities exhibiting identical physical properties have almost equi-energetic crystal structures while the most stable third polymorph exhibits distinct properties. Thereby, structure-property correlations are derived, both quantitatively and qualitatively. © 2016 The Royal Society of Chemistry.

Fulltext

CrystEngComm

Isostructural polymorphs: Qualitative insights from energy frameworks

Crystal Growth & Design

Concomitance, Reversibility, and Switching Ability of Centrosymmetric and Non-Centrosymmetric Crystal Forms: Polymorphism in an Organic Nonlinear Optical Material

Angewandte Chemie International Edition

Enantioselective Crossed Photocycloadditions of Styrenic Olefins by Lewis Acid Catalyzed Triplet Sensitization

Which Metals are Green for Catalysis? Comparison of the Toxicities of Ni, Cu, Fe, Pd, Pt, Rh, and Au Salts

Chemical Reviews

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

Harnessing sun for catalyst and sensitizer free regio- and stereo-selective [2+2] cycloaddition