A palladium-catalyzed C-H bond activation reaction, via a redox-neutral pathway, for the preparation of dihydrophenanthridine, phenanthridine, and carbazole derivatives from biaryl 2-iminoquinones is developed. The preinstalled iminoquinone was designed to act as a directing group for ortho C-H activation and an internal oxidant or a co-oxidant. This catalysis proceeded through the following sequence: C-H bond activation, coordination and insertion of activated olefins, β-hydride elimination, H-shift, insertion, and protonation or β-hydride elimination. In addition, carbazoles can be prepared efficiently by using this method without the addition of external oxidants.
Palladium-catalyzed cycloaromatization of N-acyl-2-aminobiaryls, through a sequence of ortho CÀH bond activation/alkyne insertion/meta CÀH bond activation/alkyne insertion, was developed. An efficient synthesis of multiaryl-substituted naphthalenes, N-[2-(5,6,7,8-tetraarylnaphthalen-1yl)aryl]acetamides, was demonstrated using molecular oxygen as the sole oxidant. Furthermore, through Buchwald's synthetic protocol, two compounds were converted into corresponding fluorescent carbazoles in 30-40% yield by intramolecular CÀN bond formation.
Cellulose membranes were engineered to produce hydrophobic surfaces via a simple and soft chemical process to introduce multifunctional properties of an otherwise hydrophilic cellulose surface with polymer-grafted nanosilver to form a core-shell nanostructure. A superhydrophobic domain of the polymer on cellulose was created through the amide bond formation between the anhydride units of the polymer and the aminosiloxane-functionalized cellulose through layer-over-layer formulation. This formulation was confirmed through XPS, XRD, 29Si-NMR, and FTIR studies. Further, SEM and TEM analysis revealed that short linear silver nanowires were uniformly obtained with an average diameter of 60 nm and length of 288 nm, using a mild reducing agent at 60 degrees C, which resulted in a hierarchical cellulose surface. The nanosilver colloids released from the hierarchical cellulose surface were stabilized by the polymer matrix in solution, which led to a decrease in the rate of formation of Ag+ enhancing the material's killing efficacy against microbes. This biodegradable nanocomposite-based cellulose hierarchical surface development has potential for application as superhydrophobic membranes for oil-water separation, antimicrobial activity, and pH-triggered sustained release of colloidal silver for wound healing, which could possibly be applied for use as smart bandages.
Unique dual‐emissive and deep‐blue/green fluorescent multi‐substituted 4‐azapyrenes with bathochromic shift emission, quantum yields up to 0.60 and long excited‐state lifetime were synthesized successfully by annulative π‐extension reactions. This synthesis constitutes a palladium‐catalyzed dehydrogenative annulation of N‐acyl‐2‐aminobiaryls with in situ 1,3‐diynes as a key step, giving substituted phenanthrenes via a rollover C−H bond activation, followed by Bischler‐Napieralski cyclization. Further π‐extension by superacid‐mediated cyclization produced a blue fluorescent naphtho 4‐azapyrene.
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