A General Synthesis of the Troponoid System Based on Solvolysis of 1,4-Dihydrobenzyl Tosylates

Bio-inspired formal total synthesis of (±)-bisabosqual A

A new approach was developed to construct a hexahydrobenzofurobenzopyran ring system by an oxa-[3+3], Diels–Alder reaction and oxidative aromatization. As a synthetic application, the bio-inspired formal synthesis of bisabosqual A was achieved.

Defluorodearomatization: A Photocatalytic Birch-Like Reduction That Enables C-C Bond Formation and Provides Access to Unnatural Cannabinoids

Within the framework of discovery chemistry, polyfluorination remains a synthetic challenge despite its ability to provide useful characteristics, such as a reduction in the number of hydrogen bond donors and metabolic stability. Coupling a reversal of this methodology with photocatalysis has been demonstrated to allow the rapid synthesis of previously difficult or impossible targets by starting with fluorines everywhere and selectively removing or functionalizing them. Herein, we demonstrate a novel method to synthesize 1,4-cyclohexadienes through a dearomative photocatalytic C-C coupling reaction. This allows for access to materials that are orthogonal to the selectivity of the Birch reaction and are more functional-group-tolerant. The reaction also allows the efficient synthesis of polyfluorinated cannabinoids. While the yields are modest, the access to the new chemical space provided by the reaction is unprecedented by any means. The trifluorinated analog of THC, 1-deoxy-1,2,4-trifluoro-THC, is synthesized, demonstrating the importance of discovery chemistry and the ability to explore otherwise unknown structure-activity relationships.

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

A series of derivatives of 2-hetaryl-1,3-tropolone (β-tropolone) was prepared by the acid-catalyzed reaction of 2-methylbenzoxazoles, 2-methylbenzothiazoles and 2,3,3-trimethylindoline with 3,4,5,6-tetrachloro-1,2-benzoquinone. The molecular structures of the three representative compounds were determined by X-ray crystallography. In crystal and (as shown by the DFT PBE0/6-311+G** calculations) in solution, 2-hetaryl-4,5,6,7-tetrachloro- and 2-hetaryl-5,6,7-trichloro-1,3-tropolones exist in the NH-tautomeric form with a strong resonance-assisted intramolecular N–H···O hydrogen bond. The mechanism of the formation of 1,3-tropolones in the reaction of methylene-active five-membered heterocycles with o-chloranil in acetic acid solution has been studied using density functional theory (DFT) methods. The reaction of 2-(2-benzoxa(thia)zolyl)-5,6,7-trichloro(4,5,6,7-tetrachloro)-1,3-tropolones with alcohols leads to the contraction of the seven-membered tropone ring with the formation of 2-(2-benzoxa(thia)zolyl)-6-alkoxycarbonylphenols. The molecular structure of 2-(2-ethoxycarbonyl-6-hydroxy-3,4,5-trichlorophenyl)benzoxazole has been determined by X-ray diffraction. 2-(2-Benzoxa(thia)zolyl)-6-alkoxycarbonylphenols display intense green fluorescence with anomalous Stokes shifts caused by the excited state intramolecular proton transfer (ESIPT) effects.

Biological activity of tropolone

Tropolone (1). showed strong insecticidal activity on Tyrophagus putrescentiae and Dermatophagoides farinae. The insecticidal effect of 1 on both insects was stronger than that of hinokitiol (2, 4-isopropyltropolone: major component of Thujopsis dolabrata SIEB. et ZUCC. hondai MAKINO). The insecticidal activity of both compounds was higher than that of N,N-diethyl-m-toluamide (DEET), used as a positive control. Compound 1 had potent insecticidal activity against Coptotermes formosanus, although its activity was much lower than that of commercial chloropyrifos. Like 2, 1 showed the inhibitory activity toward metalloproteases such as carboxypeptidase A, collagenase and thermolysin and their inhibitory activities were much higher than that of 1,10-phenanthroline, used as a positive control. The inhibitory activity of 1 on carboxypeptidase A was especially high, its 50% inhibitory concentrations (IC(50)) being 2.73 x 10(-6) M. This inhibitory activity was as high as that of 2 (IC(50): 2.76 x 10(-6) M). Compound 1 inhibited the growth of seven kinds of plant-pathogenic fungi and their minimum inhibitory concentration (MIC) values were in the range of 6.0-50.0 microg/ml. In particular, 1 showed strong antifungal activity on Pythium aphanidermatum IFO-32440 (MIC: 6.0 microg/ml).

Butyrophenone analogues in the carbazole series: synthesis and determination of affinities at D2 and 5-HT2A receptors

We describe a practical and efficient route for synthesis of 2-aminomethyl-1,2,3,9-tetrahydro-4H-carbazol-4-ones using an effective Fisher indole methodology. The most active compounds, 4b (QF 2003B) and 4c (QF 2004B), with pKi (5-HT2A/D2) ratio of 1.28 show an antipsychotic profile according to Meltzer's classification.