Tandem Pd-catalyzed C–C coupling/recyclization of 2-(2-bromoaryl)cyclopropane-1,1-dicarboxylates with primary nitro alkanes

Metal-Free Synthesis of 2-(per)Fluoroalkyl-3-nitro Indoles via Intramolecular Cyclization of Amides

A metal-free intramolecular cyclization of N-acyl amides for the synthesis of 3-nitro-2-(per)fluoroalkyl indoles is reported. Good functional group tolerance and a broad range of substrates are the features of this approach. The developed method is easy to operate and is suitable for the preparation of 2-difluoromethyl/trifluoromethyl/perfluoroethyl/perfluoropropyl indoles in yields of 84 to 99%. Also, the application of this protocol in the gram scale is shown.

An Exploration of Substituent Effects on the Photophysical Properties of Monobenzopentalenes

Monobenzopentalenes have received moderate attention compared to dibenzopentalenes, yet their accessibility as stable, non-symmetric structures with diverse substituents could be interesting for materials applications, including molecular photonics. Recently, monobenzopentalene was considered computationally as a potential chromophore for singlet fission (SF) photovoltaics. To advance this compound class towards photonics applications, the excited state energetics must be characterized, computationally and experimentally. In this report we synthesized a series of stable substituted monobenzopentalenes and provided the first experimental exploration of their photophysical properties. Structural and opto-electronic characterization revealed that all derivatives showed 1H NMR shifts in the olefinic region, bond length alternation in the pentalene unit, low-intensity absorptions reflecting the ground-state antiaromatic character and in turn the symmetry forbidden HOMO-to-LUMO transitions of ~2 eV and redox amphotericity. This was also supported by computed aromaticity indices (NICS, ACID, HOMA). Accordingly, substituents did not affect the fulfilment of the energetic criterion of SF, as the computed excited-state energy levels satisfied the required E(S1)/E(T1)>2 relationship. Further spectroscopic measurements revealed a concentration dependent quenching of the excited state and population of the S2 state on the nanosecond timescale, providing initial evidence for unusual photophysics and an alternative entry point for singlet fission with monobenzopentalenes.

Synthesis of 2-[2-(Ethoxymethoxy)phenyl]spiro[cyclopropane-1,2′-indene]-1′,3′-dione

An 1,3-indanedione-derived donor–acceptor cyclopropane, bearing the ethoxymethyl-protected phenolic group at the ortho-position of the donor aryl substituent, has been synthesized using a reaction sequence involving the Knoevenagel condensation of 1,3-indanedione with the corresponding protected salicylaldehyde followed by the Corey–Chaykovsky cyclopropanation of the obtained adduct with dimethylsulfoxonium methylide. The structure of the synthesized cyclopropane was unambiguously proved by single-crystal X-ray diffraction data.

Dimethyl 2-{[2-(2-Methoxy-1-methoxycarbonyl-2-oxoethyl)-4,5,7-trimethoxy-3-(2,4,5-trimethoxyphenyl)-2,3-dihydro-1H-inden-1-yl]methyl}malonate

A simple synthetic approach to dimethyl 2-{[2-(2-methoxy-1-methoxycarbonyl-2-oxoethyl)-4,5,7-trimethoxy-3-(2,4,5-trimethoxyphenyl)-2,3-dihydro-1H-inden-1-yl]methyl}malonate has been developed, based on a B(C6F5)3-induced domino dimerization of 2-(2,4,5-trimethoxyphenyl)cyclopropane-1,1-diester.

Transition-metal-free α-arylation of nitroketones with diaryliodonium salts for the synthesis of tertiary α-aryl, α-nitro ketones

Transition-metal-free α-arylation of α-nitroketones with diaryliodonium salts has been developed for the first time and applied in the synthesis of tiletamine.