Organic chemistry frontiers : an international journal of organic chemistry最新文献

Size is an important factor for vesicles, which is essential for their application, particularly in nanomedicine and nanomaterials. Unlike polymer vesicles, whose size can be controlled by the hydrophobic/hydrophilic content or the chain length, the size of supramolecular vesicles mainly depends on the assembly of the supramolecular building blocks. Herein, we describe a novel method to manipulate the size of supramolecular vesicles by regulating the assembly of hydrogen-bonding aromatic hydrazone macrocycles with different pyridinium guests. The assembly of an aromatic hydrazone macrocycle with different mono-/bi-pyridinium guests is confirmed by ¹H NMR, DOSY, MS, and TEM. This study offers a new strategy to manipulate the size of supramolecular vesicles, which might be of importance for the application of vesicles.

As an alternative metal-free amination, we report a simple and efficient annulation reaction of 1-(3,3,3-trifluoro-2-oxopropyl)pyridin-1-ium bromide and α,β-unsaturated carbonyl compounds with NH₄OAc or amines. With the developed protocol, a series of 3-trifluoromethyl aniline derivatives as the major products were obtained in good to excellent yields under Kröhnke pyridine synthesis conditions. The reaction proceeds via a cascade process involving the 1,4-Michael addition of the pyridinium ylide to an α,β-unsaturated carbonyl compound, followed by intramolecular addition of a carbanion to the keto carbonyl group to form a dienone intermediate.

The mechanism of Co(iii)-catalyzed annulation of N-chlorobenzamide with styrene was computationally studied and the effects of chiral cyclopentadienyl (Cp) ligands on enantioselectivity were investigated by using energy decomposition analysis (EDA). The spin-crossover event of Co complexes is observed in the computed energy profile. The triplet state of Co species is favored in most of the intermediates and transition states except for the styrene migratory insertion step which prefers the singlet state. The irreversible styrene migratory insertion is the enantioselectivity-determining step of the reaction. EDA results indicate that the steric effect is the dominant factor for the high-level enantiocontrol, which highlights the importance of the additional bulky substituents on the Cp ring of trisubstituted BINOL-Cp ligands.

An efficient Mn(iii)-promoted cascade reaction of tryptamine-derived isocyanides with arylboronic acids for accessing spiroindoline derivatives is described. The reaction proceeds via a radical addition/spirocyclization pathway, providing spiroindolines in good yields under mild conditions.

A reductive Sandmeyer-type sulfinylation reaction of aryldiazonium salts with sodium sulfinates is reported. The reaction takes place under photocatalysis, generating a range of valuable sulfoxides via a radical substitution pathway. Aromatic amines can also be converted to the corresponding sulfoxides via in situ diazotization in a one-pot, two-step process. The late-stage sulfinylation of drug-based amines further demonstrated the practicality of this method.

The first example of an acid-promoted difunctionalization of ketones to construct C–P and C–C bonds via a phospha-aldol-elimination is described under metal- and solvent-free conditions. The cascade α-phosphorylation and α-alkylation sequence directly converts ketones to α,α-disubstituted γ-ketone phosphine oxides, thereby providing a new strategy for the synthesis of the α,α-disubstituted γ-ketone phosphine oxide anticholinesterase skeleton in moderate to excellent yields with water as the only by-product. Detailed mechanistic experiments verified that the reaction proceeds via a TfOH-induced carbocationic intermediate formed after the α-phosphorylation of ketones.

The Ritter reaction is a powerful method for the synthesis of amides; however, the photoinduced Ritter reaction of alcohols is rarely reported. We herein report a simple and additive-free photocatalytic dehydration method for the efficient direct conversion of benzyl alcohols to the corresponding amides using an organic photocatalyst 2,4,6-triphenylpyrylium salt. Experimental and computational mechanistic analyses show that a non-conventional generation process of a carbocation is involved in this photoinduced Ritter reaction.

We describe an electrophotocatalytic tri- or difluoromethylation/cyclization cascade of alkenes with fluoromethanesulfinate salts. This external-oxidant-free oxidative cyclization proceeds under mild electrode potentials yet is robust, and it is applicable to a broad range of alkenes, either activated or unactivated, affording a diverse array of fluoromethylated heterocycles with good functional-group tolerance using the inexpensive photocatalyst eosin Y. Of note is that an unactivated olefin is generally not accommodated by previous oxidative cyclization of alkenes unless a strong chemical oxidant is present. The protocol is amenable to the late-stage diversification of complex molecular architectures as well as a gram-scale synthesis, and sunlight could serve as the light source. Preliminary mechanistic studies suggest the merger of electrolysis with the reductive quenching photocatalytic cycle of eosin Y.

Fe/S cluster catalyzed radical cascade cyclization of alkylthio-functionalized o-anilide-embedded N,S-1,6-enynes to afford thieno[3,4-b]indoles is developed. The cycloisomerization strategy offers a straightforward route to 4H-thieno[3,4-b]indoles through the 1,2-sulfur transfer and Csp³–S bond cleavage, with the formation of both an indole ring and a fused thiophene ring in one pot. In this cascade, the element sulfur acts as the oxidant to induce the single electron transfer (SET) process.