Facile Aromatic Finkelstein Iodination (AFI) Reaction in 1,3-Dimethyl-2-imidazolidinone (DMI)

A Dualistic Arrangement of a Chiral [1]Rotaxane Based on the Assembly of Two Rings and Two Rods

We demonstrate the synthesis and chiroptical properties of doubled molecules of a chiral [1]rotaxane, based on the assembly of an achiral ring of a phenylacetylene macrocycle (6PAM) and a p-phenylene ethynylene rod. Two molecules of [1]rotaxane constituted the doubled molecule through the ring fusion of 6PAMs to a 10PAM, which assured stationary occupation relative to each optically active unit. The absorption properties of the 10PAM-based doubled molecule and 6PAM-based original unit were consistently characterized by the independent existence of m-phenylene ethynylene ring(s) and p-phenylene ethynylene rod(s). Thus, molar circular dichroism (CD) was directly compared between the doubled molecule (n = 2) and the original unit (n = 1) to show that molar CD was increased more than expected by an increase in the number of units, or by an increase in absorbance. Due to the invariance of the configuration and the relative occupation of two units arranged adjacent to each other in 10PAM, one more comparison was available with an isomeric molecule of two rings and two rods in a threaded-and-unthreaded form. The additional arrangement of an optically inactive unit in an unthreaded form also led to an increase in molar CD, compared to that of the original chiral unit in a threaded form.

Synthesis, Biosynthesis, and Biological Activity of Diels-Alder Adducts from Morus Genus: An Update

The plants of the Moraceae family are producers of a great variety of polyphenolic natural products. Among these, the Diels-Alder type adducts (DAAs) are endowed with a unique cyclohexene scaffold, since they are biosynthesized from [4+2] cycloaddition of different polyphenolic precursors such as chalcones and dehydroprenyl polyphenols. To date, more than 150 DAAs have been isolated and characterized from Moraceous and related plants. The main source of DAAs is the mulberry root bark, also known as "Sang-Bai-Pi" in Traditional Chinese Medicine, but they have also been isolated from root bark, stem barks, roots, stems or twigs, leaves, and callus cultures of Moraceous and other related plants. Since 1980, many biological activities of DAAs have been identified, including anti-HIV, antimicrobial, anti-inflammatory, and anticancer ones. For these reasons, natural DAAs have been intensively investigated, and a lot of efforts have been made to study their biosynthesis and to establish practical synthetic access. In this review, we summarized all the updated knowledge on biosynthesis, chemoenzymatic synthesis, racemic and enantioselective total synthesis, and biological activity of natural DAAs from Moraceous and related plants.

Nonclassical Phenyl Bioisosteres as Effective Replacements in a Series of Novel Open-Source Antimalarials

The replacement of one chemical motif with another that is broadly similar is a common method in medicinal chemistry to modulate the physical and biological properties of a molecule (i.e., bioisosterism). In recent years, bioisosteres such as cubane and bicyclo[1.1.1]pentane (BCP) have been used as highly effective phenyl mimics. Herein, we show the successful incorporation of a range of phenyl bioisosteres during the open-source optimization of an antimalarial series. Cubane (19) and closo-carborane (23) analogues exhibited improved in vitro potency against Plasmodium falciparum compared to the parent phenyl compound; however, these changes resulted in a reduction in metabolic stability; unusually, enzyme-mediated oxidation was found to take place on the cubane core. A BCP analogue (22) was found to be equipotent to its parent phenyl compound and showed significantly improved metabolic properties. While these results demonstrate the utility of these atypical bioisosteres when used in a medicinal chemistry program, the search to find a suitable bioisostere may well require the preparation of many candidates, in our case, 32 compounds.

Facile Redox-Induced Aromatic-Antiaromatic Interconversion of a β-Tetracyano-21,23-Dithiaporphyrin under Ambient Conditions

Facile redox-induced aromatic-antiaromatic interconversions were accomplished by using β-tetracyano-21,23-dithiaporphyrin (CN₄ S₂ Por). Introduced cyano groups not only increased the reduction potential of the porphyrin core but also stabilized the antiaromatic isophlorin (CN₄ S₂ Iph) by π conjugation. The reduction of CN₄ S₂ Por with hydrazine in polar solvents quantitatively affords CN₄ S₂ Iph, even under ambient conditions. CN₄ S₂ Iph retains a nearly planar conformation and exhibits considerable antiaromaticity. Aerobic oxidation of CN₄ S₂ Iph to CN₄ S₂ Por occurs in nonpolar solvents. This study was conducted to contribute to the understanding of the structure-antiaromaticity relationship.

Upper-rim functionalization and supramolecular polymerization of a feet-to-feet-connected biscavitand

An octaiodobiscavitand was synthesized via an aromatic Finkelstein iodination reaction in good yield. An octa-functionalized biscavitand self-assembled to form a supramolecular polymer in the solid state.

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: A Review

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

Photocatalyzed iron-based ATRP of methyl methacrylate using 1,3-dimethyl-2-imidazolidinone as both solvent and ligand

A simple photocatalyzed Fe-based ATRP of MMA was conducted under UV irradiation using the “green” solvent DMI as both the solvent and ligand.

Total Synthesis of (±)-Kuwanol E

The total synthesis of the Diels-Alder-type adducts (±)-kuwanol E and the heptamethyl ether derivative of (±)-kuwanon Y has been accomplished via a convergent strategy involving 2'-hydroxychalcone 6 or 9 and dehydroprenylstilbene 7, in nine steps. The synthesis features, as a key step, a Lewis acid-mediated biomimetic intermolecular Diels-Alder [4+2] cycloaddition for the construction of the cyclohexene skeleton with three stereogenic centers. Notably, the endo/exo diastereoselectivity of the reaction proved to be temperature-controlled.

A General Copper-Catalyzed Vinylic Halogen Exchange Reaction

An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N'-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.

The regioselective iodination of quinolines, quinolones, pyridones, pyridines and uracil

A radical based direct C–H iodination protocol for quinolines, quinolones, pyridones, pyridines, and uracil has been developed.