Polycyclic Aromatic N-Ethoxycarbonyl Thioamide S-Oxides and Their Triflic Acid Promoted Cyclization to Fluorescent Thiophene Imine-Fused Arenes

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

This review surveys recent progress in the chemistry of polycyclic heteroaromatic molecules with a focus on structural diversity and synthetic methodology. The article covers literature published during the period of 2016-2020, providing an update to our first review of this topic (Chem. Rev. 2017, 117 (4), 3479-3716).

Chemoselective Ullmann Reaction of α-Trisubstituted Thioamides: Synthesis of Novel 2-Iminobenzothiolanes

New classes of unexplored benzo[b]thiolanes are synthesized from trisubstituted thioamides through copper-catalyzed intramolecular S-arylation of thioamides for the first time. This method provides good to excellent yields with fully controlled chemoselectivity. Unusually, iminobenzo[b]thiolanes are very stable under mild acidic conditions. A plausible mechanism is proposed for the chemoselective S-arylation process.

Pine Rosin as a Valuable Natural Resource in the Synthesis of Fungicide Candidates for Controlling Fusarium oxysporum on Cucumber

To improve the effect of pine rosin in plant fungicides, four series of dehydroabietyl-1,3,4-thiadiazole derivatives from the natural product rosin were synthesized. Based on the evaluation of the in vitro antifungal activity against Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium oxysporum, and Magnaporthe oryzae, rosin-based 1,3,4-thiadiazole compounds containing thiophene heterocycles were screened. Notably, compound 3e [dehydroabietyl-(1,3,4-thiadiazol-2-yl)-5-nitrothiophene-2-carboxamide] exhibited excellent antifungal property against F. oxysporum with an EC₅₀ of 0.618 mg/L, which was lower than that of the positive control carbendazim (0.649 mg/L). The in vivo antifungal activity results showed that 3e exerted a protective effect on cucumber plants. Physiological and biochemical studies showed that the primary mechanism of action of compound 3e on F. oxysporum was it changed the mycelial morphology, increased the cell membrane permeability, and inhibited the synthesis of ergosterol in the mycelia. Furthermore, the quantitative structure-activity relationship studies revealed that the frontier orbital energy in the molecule had a key role in the antifungal activity through the conjugation and electrostatic interaction between compound 3e and the receptors of the target. Thus, the present study highlighted the application of rosin-based fungicidal candidates and exploited efficient plant pesticides for sustainable crop production.

The copper-catalyzed synthesis of (Z)-2H-naphtho[1,8-bc]thiophenes with solid emission

In recent years, one of the main research interests of our group has been the construction of 6/5 π-systems through the regioselective conversion of parallel alkynes in naphthalene with the aim of exploiting potential fluorescent materials. Herein, the copper-catalyzed synthesis of polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes from 8-halo-1-ethynylnaphthalenes using potassium ethylxanthate as the sulfur source is reported. In this protocol, a series of thiophene-fused 6/5 π-system compounds was synthesized via copper-catalyzed Ullmann-type C(aryl)-S bond formation and the α-addition of an alkyne bond with high selectivity and in high yields. The synthesized polysubstituted (Z)-2H-naphtho[1,8-bc]thiophenes exhibited solid emission, which made them potential candidates for use in optoelectronic conjugated materials. By using DMSO/D2O (3 : 1) as the reaction solvent, the deuterated products could be obtained in good yields under standard conditions.

Rapid construction of cyclopenta[b]naphthalene frameworks from propargylic alcohol tethered methylenecyclopropanes

We have developed a new synthetic methodology for the rapid construction of cyclopenta[b]naphthalene frameworks from the reaction of propargylic alcohol tethered methylenecyclopropanes with mesyl chloride in the presence of triethylamine through cascade cyclization. The reaction can be performed under mild conditions without the use of transition metals, affording the target products in moderate to good yields, and this cyclization reaction process can be scaled up to a gram-scale synthesis.

Transition metal-free, chemoselective arylation of thioamides yielding aryl thioimidates orN-aryl thioamides

A highlyS-selective arylation of thioamides provided efficient access to aryl thioimidates.