Friedel-Crafts Reactions with N-Heterocyclic Alcohols.

N-Heterocyclic alcohols are shown to be excellent substrates for superacid-promoted Friedel-Crafts reactions. The N-heterocyclic alcohols ionize to produce reactive, dicationic intermediates which provide good to excellent yields of arylation products.

Zero-Background Small-Molecule Sensors for Near-IR Fluorescent Imaging of Biomacromolecular Targets in Cells.

In this study, we report a general approach to the design of a new generation of small-molecule sensors that produce a zero background but are brightly fluorescent in the near-IR spectral range upon selective interaction with a biomolecular target. We developed a fluorescence turn-on/-off mechanism based on the aggregation/deaggregation of phthalocyanine chromophores. As a proof of concept, we designed, prepared, and characterized sensors for in-cell visualization of epidermal growth factor receptor (EGFR) tyrosine kinase. We established a structure/bioavailability correlation, determined conditions for the optimal sensor uptake and imaging, and demonstrated binding specificity and applications over a wide range of treatment options involving live and fixed cells. The new approach enables high-contrast imaging and requires no in-cell chemical assembly or postexposure manipulations (i.e., washes). The general design principles demonstrated in this work can be extended toward sensors and imaging agents for other biomolecular targets.

Photochemistry with Plane-Polarized Light: Controlling Photochemical Reactivity via Spatially Selective Excitation.

Photochemical reactions are intrinsically difficult to control because they involve high-energy excited-state species. Herein we report a novel approach toward controlling photochemical reactions via using the spatially selective excitation of specific electronic transitions. This can be performed using photochemical irradiation with the plane-polarized light of a photoreactive compound uniformly aligned in a nematic liquid-crystalline (LC) medium. Having chosen cyclopropenone photodecarbonylation as a proof-of-concept reaction, we demonstrated that it could be controlled via changing an angle between the incident light polarization plane and the LC director. We showed that two specific partially forbidden electronic transitions were mostly responsible for this photochemical reaction. We envision that this simple general method can be useful in experimental studies of the fundamental details of various photochemical processes and can help to increase the selectivity of photochemical transformations.

Superelectrophiles: Recent Advances.

Superelectrophiles are reactive species that often carry multiple positive charges. They have been useful in numerous synthetic methods and they often exhibit highly unusual reactivities. Recent advances in superelectrophile chemistry are discussed in this review.