Erica Benedetti

Synthesis and Photophysical Properties of a Series of Cyclopenta[b]naphthalene Solvatochromic Fluorophores

The synthesis and photophysical properties of a series of naphthalene-containing solvatochromic fluorophores are described within. These novel fluorophores are prepared using a microwave-assisted dehydrogenative Diels-Alder reaction of styrene, followed by a palladium-catalyzed cross coupling reaction to install an electron donating amine group. The new fluorophores are structurally related to Prodan. Photophysical properties of the new fluorophores were studied and intriguing solvatochromic behavior was observed. For most of these fluorophores, high quantum yields (60-99%) were observed in methylene chloride in addition to large Stokes shifts (95-226 nm) in this same solvent. As the solvent polarity increased, so did the observed Stokes shift with one derivative displaying a Stokes shift of ~300 nm in ethanol. All fluorophore emission maxima, and nearly all absorption maxima were significantly red-shifted when compared to Prodan. Shifting the absorption and emission maxima of a fluorophore into the visible region increases its utility in biological applications. Moreover, the cyclopentane portion of the fluorophore structure provides an attachment point for biomolecules that will minimize disruptions of the photophysical properties.

Gold(I)-Catalyzed Cyclization of β-Allenylhydrazones: An Efficient Synthesis of Multisubstituted N-Aminopyrroles

The gold(I)-catalyzed cycloisomerization of β-allenylhydrazones provides an efficient access to multisubstituted N-aminopyrroles, which are obtained in good to excellent yields. This new intramolecular cyclization method can be applied either to alkyl- or aryl-substituted allenes. The reaction proceeds under mild conditions with short reaction times through a selective intramolecular 1,2-alkyl or -aryl migration extending the general scope of the reaction.

DNA vs. Mirror‐Image DNA: A Universal Approach to Tune the Absolute Configuration in DNA‐Based Asymmetric Catalysis

Mirror mirror on the wall: By taking advantage of the unique structural features of L-DNA, the first examples of left-helical enantioselective induction in the field of DNA-based asymmetric catalysis were realized. Most importantly, this approach is the only one that allows a reliable and predictable access to both enantiomers for any given reaction.

A Thermal Dehydrogenative Diels–Alder Reaction of Styrenes for the Concise Synthesis of Functionalized Naphthalenes

Functionalized naphthalenes are valuable building blocks in many important areas. A microwave-assisted, intramolecular dehydrogenative Diels-Alder reaction of styrenyl derivatives to provide cyclopenta[b]naphthalene substructures not previously accessible using existing synthetic methods is described. The synthetic utility of these uniquely functionalized naphthalenes was demonstrated by a single-step conversion of one of these cycloadducts to a fluorophore bearing a structural resemblance to Prodan.

Attachable Solvatochromic Fluorophores and Bioconjugation Studies

The synthesis and utility of attachable cyclopenta[b]naphthalene solvatochromic fluorophores related to Prodan are described. Two fluorophores were selected for functionalization and bioconjugation studies. The skeletons were chemically modified to include reactive functional groups and showed minimal alteration of the optical properties when compared to the parent dyes. The functionalized fluorophores were covalently attached to the carboxyl group of a fatty acid, and azido- and thiol-containing amino acids, demonstrating their potential for labeling biomolecules.

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Synthesis and photophysical studies of through-space conjugated [2.2]paracyclophane-based naphthalene fluorophores

In this work we report a straightforward method for the synthesis of a new class of small organic fluorophores bearing both [2.2]paracyclophane and naphthalene subunits using an intramolecular dehydrogenative Diels–Alder reaction as a key step. These compounds are characterized by a compact three-dimensional structure as well as through-space conjugated push–pull systems, and possess interesting spectroscopic characteristics that may be useful for the development of innovative chemical probes and optical sensors.