Brønsted acid TfOH-mediated [3 + 2] cycloaddition reactions of diarylvinylidenecyclopropanes with nitriles

Synthesis and Lewis Acid Properties of Neutral Silver(III) Adducts Containing the AgIII(CF3)3 Moiety

The acetonitrile AgIII complex [AgIII(CF3)3(NCCH3)] (2) has been reported independently by Eujen and Naumann in the last century, albeit with intriguing NMR discrepancy. In their reports, 2 was claimed to be obtained starting from either [AgIII(CF3)3Cl]- (3⋅Cl) or [AgIII(CF3)4]- (1) via halide abstraction using AgNO3 or acidic treatment, resp. These two synthetic routes are herein reinvestigated. The feasibility of Naumann's method is demonstrated, thus providing 2 yet accompanied by its s-triazinyl derivative [AgIII(CF3)3(C6H9N3)] (2'). The formation of 2' is unprecedented and was thereby investigated. Both 2 and 2' were isolated in pure fashion and fully characterized. In turn, halide extraction from 3⋅Cl leads to the AgIII-ONO2 anion 5 instead of 2, as evidenced by NMR spectroscopy, EA and Sc-XRD.

Synthesis of 1-pyrroline derivatives via cyclization of terminal alkynes with 2-azaallyls

An efficient transition-metal-free cyclization reaction to prepare 1-pyrroline derivatives bearing various functional groups is described. In this method, a simple combination of a base and a solvent allows the cyclization reaction of terminal alkynes and 2-azaallyls to be carried out efficiently under mild and metal-free conditions. This cyclization reaction will provide an efficient method for the synthesis of medicinally relevant polysubstituted and multifunctionalized pyrrolines.

Palladium catalyzed divergent cycloadditions of vinylidenecyclopropane-diesters with methyleneindolinones enabled by zwitterionic π-propargyl palladium species

A palladium-catalyzed divergent synthesis of spirooxindoles fused with a five- or a six-membered ring by a cycloaddition reaction of vinylidenecyclopropane-diesters with methyleneindolinones was disclosed. This protocol features an in situ generated unprecedented zwitterionic π-propargyl palladium species in cycloaddition reactions and a switchable process between (3+2) and (4+2) cycloadditions by changing the phosphine ligand.

Unprecedented Regio- and Stereoselective Synthesis of Pyrene-Grafted Dispiro[indoline-3,2'-pyrrolidine-3',3″-indolines]: Expedient Experimental and Theoretical Insights into Polar [3 + 2] Cycloaddition

A series of dispiro[indoline-3,2'-pyrrolidine-3',3″-indolines] was synthesized via a multicomponent polar [3 + 2] cycloaddition (32CA) reaction of isatin derivatives, sarcosine and (E)-3-(2-oxo-2-(pyren-1-yl)ethylidene)indolin-2-one derivatives. The regio- and stereochemistries of the cycloadducts were established on the basis of one-dimensional (1D) (1H-, 13C-, 13C-CRAPT NMR) and two-dimensional (2D) homonuclear and heteronuclear correlation NMR spectrometry experiments (1H-1H gDQFCOSY, 13C-1H-HSQCAD, 13C-1H-HMBCAD, 1H-1H-ROESYAD). The molecular mechanism and regio- and stereoselectivities of the cycloaddition (CA) reaction have been investigated utilizing a density functional theory (DFT) method and were thoroughly explained based on the transition-state stabilities and global/local electrophilicity/nucleophilicity reactivity indices of the reactants.

Synthesis of Vinylene-Linked Covalent Organic Frameworks from Acetonitrile: Combining Cyclotrimerization and Aldol Condensation in One Pot

Combining two or more consecutive reactions in one pot is a common approach for process development, as such a method involves cheap starting materials and allows in situ generation of a reactive intermediate, to undergo further reaction, without isolation. Herein, we report the synthesis of a vinylene-linked (-CH═CH-) covalent organic framework, COF-701, directly from acetonitrile, a cheap commodity solvent, by combining/telescoping two consecutive reactions-cyclotrimerization of nitrile and subsequent aldol condensation with aldehydes-in one pot. Acetonitrile is trimerized to generate protonated 2,4,6-trimethyl-s-triazine tautomers in situ, which undergo Aldol condensation with 4,4'-biphenyldicarbaldehyde in one pot to form crystalline COF-701. COF-701 is obtained as a polycrystalline powder and possesses permanent microporosity and a BET surface area (SA_BET) of 736 m²·g^-1. This strategy can be further extended to generate other porous vinylene-linked frameworks.

Triazine-Based Cationic Leaving Group: Synergistic Driving Forces for Rapid Formation of Carbocation Species

A new triazine-based cationic leaving group has been developed for the acid-catalyzed alkylation of O- and C-nucleophiles. There are two synergistic driving forces, namely, stable C═O bond formation and charge-charge repulsive effects, involved in the rapid generation of the carbocation species in the presence of trifluoromethanesulfonic acid (∼200 mol %). Considerable rate acceleration of benzylation, allylation, and p-nitrobenzylation was observed as compared to the reactions with less than 100 mol % of the acid catalyst. The triazine-based leaving group showed superior p-nitrobenzylation yield and stability in comparison to common leaving groups, trichloroacetimidate and bromide. A plausible reaction mechanism (the cationic leaving group pathway) was proposed on the basis of mechanistic and kinetic studies, NMR experiments, and calculations.

Heterocycles from methylenecyclopropanes

The discovery of a series of novel organic reactions has made methylenecyclopropanes (MCPs) some of the most popular building blocks in synthetic organic chemistry during the past two decades. Among reported works, the construction of heterocycles from MCPs has highlighted new synthetic methodologies that afford more opportunities for the quick synthesis of elaborately substituted products, and this should draw a great deal of attention. However, reviews in this area are insufficient, and the latest monograph on heterocycle synthesis from MCPs was published 12 years ago. This review aims to summarize the novel organic reactions of MCPs to produce heterocycles published in recent years, which have provided specific and powerful tools for organic synthesis.

Diaryl Selenide Catalyzed Vicinal Trifluoromethylthioamination of Alkenes

An efficient approach to vicinal trifluoromethylthioamination of alkenes with a broad substrate scope catalyzed by electron-rich diaryl selenide has been developed. This intermolecular amination strategy was successfully applied to SCF3-esterification of alkenes using weak acids as nucleophiles.

Copper(i)/Lewis acid triggered ring-opening coupling reaction of cyclopropenes with nitriles

A ring-opening coupling reaction of D–A cyclopropenes and nitriles is described for the facile synthesis of γ-amino ketones.