The first stereoselective synthesis of the natural product, rotenone

Optimization of Osthole as a Pesticide Candidate: Synthesis, Crystal Structures, and Agrochemical Properties of Acrylate Derivatives of Isopropenyl 2,3-Dihydrobenzofurans

For high-value-added application of osthole derivatives as a pesticide candidate in crop protection, by the use of osthole as a lead compound, a series of novel acrylate derivatives of isopropenyl 2,3-dihydrobenzofurans were prepared by the successive bromination, rearrangement, and esterization reactions. Three-dimensional structures of four compounds were determined by single-crystal X-ray diffraction. The possible mechanism for construction of this new isopropenyl 2,3-dihydrobenzofuran skeleton from the osthole was presented. Against Plutella xylostella Linnaeus, compound 32 (R = PhCH2CH2) displayed 3.5-fold potent insecticidal activity of osthole. Against Tetranychus cinnabarinus Boisduval, compound 40 (LC50: 0.165 mg/mL; R = (CH2)13CH3) showed 8.3-fold pronounced acaricidal activity of osthole (LC50: 1.367 mg/mL); notably, its control effect can be comparable to that of the commercial acaricide spirodiclofen. Additionally, the scanning electron microscopy imaging method demonstrated that compound 40 can destroy the stratum corneum of T. cinnabarinus. Compound 40 can be further explored as a lead acaricidal agent.

Asymmetric [2+2] photocycloaddition via charge transfer complex for the synthesis of tricyclic chiral ethers

The asymmetric synthesis of chiral polycyclic ethers by an intramolecular [2+2] photocycloaddition is described. This process proceeded through a photocatalytically active iminium ion-based charge transfer (CT) complex under visible light irradiation. In this way a stereocontrolled [2+2] photocycloaddition is enabled leading to tricyclic products with good enantiomeric ratios.

Synthesis of 4-Acylchromene via Highly Chemoselective Iodine-Catalyzed Cyclization of Alkynylarylether Dimethylacetals

4-Acylchromene is an important core structure found in bioactive natural products and bioactive synthetic compounds. Moreover, this core structure is frequently used as a key precursor for the synthesis of more complex molecules. In this work, we discovered that a combination of acetone and catalytic I₂ could lead to selective activation of acetal in alkynylarylether dimethylacetal substrates while alkyne moiety remained intact. This activation of acetal led to the generation of oxonium ion intermediate which triggered intramolecular cyclization and elimination of methanol to provide the desired 4-acylchromene as the sole product in up to 95% yield. Moreover, this method could be applied in a broad range of substrates under a mild and metal-free catalytic conditions for the synthesis of 4-acylchromene derivatives.

Recent Advances in Phthalan and Coumaran Chemistry

Oxygen-containing heterocycles are common in biologically active compounds. In particular, phthalan and coumaran cores are found in pharmaceuticals, organic electronics, and other useful medical and technological applications. Recent research has expanded the methods available for their synthesis. This Minireview presents recent advances in the chemistry of phthalans and coumarans, with the goal of overcoming synthetic challenges and facilitating the applications of phthalans and coumarans.

Concise Total Synthesis of (±)-Deguelin and (±)-Tephrosin Using a Vinyl Iodide as a Key Building Block

A concise and protecting-group-free total synthesis of the antiproliferative natural product (±)-deguelin (2) was accomplished in four steps and 62% overall yield from commercially available precursors. The key transformation employed a vinyl iodide as the pivotal building block to construct the 4-acylchromene substructure present in deguelin. Subsequent Cu₂O-mediated α-hydroxylation of deguelin (2) afforded tephrosin (3) in 90% yield.