An unconventional route to an ambipolar azaheterocycle and its in situ generated radical anion

Rhodium(II)-Catalyzed Alkynyl Carbene Insertion into N-H Bonds

The first insertion of an alkynyl carbene into N-H bonds under Rh-catalysis is developed. Alkynyl hydrazone carboxylates are used as donor-acceptor carbene precursors and are exquisitely inserted into the N-H bonds of various amines, amides, and 1,2-diamines. A wide variety of 3-alkynyl 3,4-dihydroquinoxalin-2(1H)-ones and densely functionalized α-alkynyl α-amino esters are obtained in good to excellent yields. Further, chemoselective N-H insertion reactions, mechanistic studies, and various synthetic transformations for obtaining valuable heterocycles are demonstrated.

4nπ Stable Multitasking Azapentacene: Acidochromism, Hole Mobility, and Visible Light Photoresponse

Herein, we describe the synthesis, characterization, and optoelectronic investigation of a stable 4nπ dihydrotetraazapentacene derivative. The neutral dihydrotetraazapentacene contains a 24π-conjugated N-heteroacene core with two phenyl pendants appended thereof. The exceptional stability of this formally antiaromatic π-system is attributed to the fused dihydropyrazine ring, which has ethenamine (enamine) conjugations, and hence, the π-electrons delocalize over the nearly planar azapentacene core to endow with a global aromatic characteristic. The embedded dihydropyrazine also offers an additional Clar's sextet with enhanced aromaticity. The present dihydrotetraazapentacene can be considered as a multitasking N-heteroacene, which showed photoresponsive nature under visible light illumination, acidochromism in solution, and p-type charge transport with an appreciable field-effect hole mobility of 0.02 cm² V^-1 s^-1 and a bulk p-type mobility of 0.98 × 10^-4 cm² V^-1 s^-1 in the space charge-limited regime of operation measured in the hole-only device. Nucleus-independent chemical shift calculation, anisotropy of the induced current density plot, and anisotropic mobility calculation were performed to support the experimental findings.