Sweet and low: Two sugar‐based supergelators can congeal oils to produce highly transparent gels with glass‐like refractive indices showing low UV transmittance and high visible transmittance and remarkable self‐healing properties. This unique blend of properties can be exploited to make soft optical devices from these gels.
The visible-light-accelerated oxo-azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap) ]Cl or [Cu(dap)Cl ] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. Cu is proposed as the catalytically active species, which upon coordinating azide will undergo light-accelerated homolysis to form Cu and azide radicals. This activation principle (Cu -X→Cu +X ) opens up new avenues for copper-based photocatalysis.
A new class of organogelators having a cyclohexane-1a,3a-diol motif capable of congealing non-polar liquids was developed. These gelators underwent crystallization at low concentration and gelation above the critical gelation concentration (CGC) in the same solvent. The crystals and gel fibers were analyzed by single crystal XRD and PXRD respectively, which revealed their different modes of assembly. The XRD studies and thermogravimetric analysis (TGA) confirmed that the crystals contain a water of crystallization whereas the gel fibers do not. A systematic study revealed that when the concentration of the gelator exceeds that of adventitious water in the solvent, it congeals the solvent and when the concentration of the gelator is less than water, it undergoes crystallization. This unprecedented stoichiometric sensing behavior in deciding the mode of self-assembly offers a handle to opt between mutually competing gelation and crystallization. We have confirmed that the system can be biased to congeal or crystallize by varying the amount of water.
A visible-light-mediated radical
tandem cyclization of ortho-isocyano-α-bromo
cinnamates to 2-substituted
indole-3-glyoxylates is achieved by formation of both C–C/C–S
and C–O bonds. The reaction proceeds through a hitherto unprecedented
bromine- or methoxy-group-promoted umpolung back electron transfer
from an α-carbonyl radical to the photocatalyst. This method
allows preparation of diverse 2-arylated or 2-thioarylated indole-3-glyoxylates.
The glyoxylate group installed in the products can be utilized for
several biologically relevant manipulations.
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