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A novel diastereodivergent tricyclization of isocyanoacetates with o-quinone methides was accomplished for the efficient synthesis of chromeno[2,3-b]chromene derivatives. All three reactive centers of isocyanoacetate reacted sequentially with two o-QMs, affording the products with four adjacent stereocenters in a diastereoselective manner. The asymmetric version was preliminarily investigated. [ABSTRACT FROM AUTHOR]

An efficient, straightforward and general method for the de novo synthesis of highly functionalized 4-fluoropyridines was developed via a cooperative copper- and base-catalyzed [3+3] cycloaddition of active methylene isocyanides with difluorocyclopropenes. The resulting 4-fluoropyridines can be readily diversified by various nucleophiles. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COF) with periodic porous structures and tunable functionalities are a new class of crystalline polymers connected via strong covalent bonds. Constructing COF materials with high stability and porosity is attracting and essential for COFs' further functional exploration. In this work, two new covalent organic frameworks (TTA‐TMTA‐COF and TTA‐FMTA‐COF) with high surface area, large pore volume, and excellent chemical stability toward harsh conditions are designed and synthesized by integrating the methoxy functional groups into the networks. Both two COFs are further employed for iodine removal since radioactive iodine in nuclear waste has seriously threatened the natural environment and human health. TTA‐TMTA‐COF and TTA‐FMTA‐COF can capture 3.21 and 5.07 g g−1 iodine, respectively. Notably, the iodine capture capacity for iodine of TTA‐FMTA‐COF does not show any decline after being recycled five times. These results demonstrate both COFs possess ultrahigh capacity and excellent recyclability. [ABSTRACT FROM AUTHOR]

Two bio‐based organic photocatalysts have been prepared for visible light‐induced atom transfer radical polymerization (ATRP). Renewable and abundant cellulose grafted with organic dyes is chosen as the photocatalyst to initiate polymerization via the reductive quenching process. Kinetic study and light on/off reaction demonstrate the "living"/controlled nature of the polymerization by light. Block copolymers can be achieved by using the PMMA as a macroinitiator to reinitiate the polymerization of other vinyl monomers, which shows highly preserved Br chain‐end functionality in the synthesized polymers. Moreover, the bio‐based catalyst can be recycled to catalyze polymerization in a controlled manner for three times. This strategy provides a metal‐free recyclable catalytic platform for visible light‐induced ATRP. [ABSTRACT FROM AUTHOR]

Tandem cyclization‐annulation of tosylmethyl isocyanide and isocyanoacetate with 2‐methyleneaminochalcones as aza‐1,5‐dielectrophiles has been successfully developed. These domino transformations feature simultaneous formation of three bonds and two rings in a single operation, and represent novel protocols for the expedient synthesis of both aromatic and partially aromatic pyrrolo[2,3‐c]quinoline derivatives from readily available precursors under metal‐free conditions. Notably, tetrahydro‐3H‐pyrrolo[2,3‐c]quinolones that bear three adjacent stereocenters were obtained in a highly diastereoselective manner. [ABSTRACT FROM AUTHOR]

Abstract: A silver‐catalyzed [5+1] annulation of o‐acylaryl isocyanides with ammonium acetate and hydroxlamine was developed for the efficient and practical synthesis of quinazolines and quinazoline 3‐oxides in good to excellent yields, respectively. The domino process involved an unprecedented isocyanide insertion into the N−H bond of ammonia or hydroxylamine and followed by condensation reaction at ambient conditions. [ABSTRACT FROM AUTHOR]

Abstract: A novel rhodium(III)‐catalyzed synthesis of 2‐(trifluoromethyl)‐dibenzopyranones from easily available 4‐(trifluoromethyl)‐p‐quinols and N‐methoxyarylamides is described. Rhodium(III)‐catalyzed formal anti‐Michael addition was proposed to be a crucial step in this [3+3] annulation with N‐methoxyarylamides as effective 1,3‐dipoles, providing a concise and efficient approach for the construction of trifluoromethyl‐containing dibenzopyranones under mild reaction conditions. [ABSTRACT FROM AUTHOR]

A silver-catalyzed aerobic oxidative [3+2] cycloaddition of azomethine ylides with aryl or heteroaryl isocyanides has been developed. The reaction represents a novel protocol for the efficient and practical synthesis of 1,2-diarylimidazoles bearing a broad range of substituents in good to excellent yields under mild conditions. The practicability of this cycloaddition was shown by a gram-scale synthesis and a double cycloaddition for the construction of highly conjugated polyarylimidazole systems. [ABSTRACT FROM AUTHOR]

A silver-catalyzed chemoselective [4+2] annulation of aryl and heteroaryl isocyanides with α-substituted isocyanoacetamides was developed for the facile and efficient synthesis of 2-aminoquinolones, naphthyridines, and phenanthrolines. A mechanism for this multistep domino reaction is proposed on the basis of a 13C-labeling experiment, according to which an unprecedented chemoselective heterodimerization of two different isocyanides generates an α-amidoketenimine intermediate, which undergoes 1,3-amino migration to form an α-imidoylketene, followed by 6 π electrocyclization. [ABSTRACT FROM AUTHOR]

A DBU-catalyzed aerobic oxidative Robinson annulation of 2-isocyanochalcones with active methylene ketones was developed for the expedient synthesis of phenanthridines in high to excellent yields. This unprecedented multistep domino reaction represents a new strategy for the construction of this tricyclic scaffold by the sequential formation of two rings and three C–C bonds in a single operation at room temperature. [ABSTRACT FROM AUTHOR]

A new three-component reaction, namely condensation–anti-Michael addition–aromatization, enabling the construction of benzylic compounds is disclosed. This reaction can not only act as an alternative approach to regioselective Csp2–H trifluoromethylation of arenes through an “aromatic to be” strategy, but also provides a simple, convenient, step-economic, and practical strategy for the in situ generation of electrophilic p-(trifluoromethyl)benzyl species under extremely mild conditions. [ABSTRACT FROM AUTHOR]

Review: 292 refs. [ABSTRACT FROM AUTHOR]

This first formal [3+2] cycloaddition of α-trifluoromethyl-3-indolylmethanol silyl ethers and acyclic ketene dithioacetals furnishes trifluoromethylated cyclopenta[b]indoles. [ABSTRACT FROM AUTHOR]

A novel diastereodivergent tricyclization of isocyanoacetates with o -quinone methides was accomplished for the efficient synthesis of chromeno[2,3- b ]chromene derivatives. All three reactive centers of isocyanoacetate reacted sequentially with two o -QMs, affording the products with four adjacent stereocenters in a diastereoselective manner. The asymmetric version was preliminarily investigated.

An ionic cascade insertion/cyclization reaction of thia-/selena-functionalized arylisocyanides has been successfully developed for the efficient and practical synthesis of 2-halobenzothiazole/benzoselenazole derivatives. This synthetic protocol, incorporating a halogen atom when forming the five-membered ring of benzothia/selenazoles, is different from the existing ones, where halogenation of the preformed benzothia/selenazole precursors happens. Additionally, a facile access to 2-aminobenzothiazoles is also achieved by the one-pot cascade reaction of 2-isocyanoaryl thioethers, iodine, and amines.

A catalyst-free chemoselective trimerization reaction of readily available isocyanides is described. This domino reaction provides facile access to a wide range of 2-(indol-2-yl)-quinolines and 2-(indol-2-yl)-pyridines in moderate to excellent yields. A "head to head" heterodimerization of two isocyanides is proposed as the key step of this reaction.

A formal [1 + 2 + 3] annulation of methyleneindolinones with o-alkenyl arylisocyanides has been developed for the general and efficient synthesis of both symmetrical and unsymmetrical indolo[3,2- b]carbazoles. The chemoselectivity of this domino reaction was tuned by a tethered alkenyl group, which enables successive formation of three new bonds and two rings from readily accessible starting materials in a single operation. Furthermore, this methodology was used as a key step in the synthesis of the alkaloid malasseziazole C.

A new anion relay enabled [3 + 3]-annulation of active methylene isocyanides and conjugated ene-yne-ketones was developed for the efficient and straightforward synthesis of biologically valuable furo[3,2-c]pyridine derivatives. In this transformation, a sequential through-bond and through-space anion relay chemistry cascade is involved, which is initiated by an intermolecular Michael addition. Three new bonds and two rings are sequentially constructed from readily available acyclic precursors.

A tandem bicyclization of azomethine ylides with methyleneaminochalcones was developed for the straightforward and facile synthesis of 2-substituted polyfunctionalized pyrrolo[2,3-c]quinolines. Both an unusual reactivity profile of azomethine ylide and a novel strategy for the construction of the tricyclic framework by the successive construction of the pyridine and pyrrole rings were exhibited in this domino reaction. Two intermediates are isolated in the control experiments, and thus a tandem bicyclization/elimination/oxidative aromatization process is proposed for the reaction mechanism.

An unprecedented chemoselective double annulation of α-trifluoromethylated isocyanides with o-acylaryl isocyanides has been developed. This new reaction provides a rapid, efficient, and complete atom-economic strategy for the synthesis of trifluoromethylated oxadiazino[3,2-a]indoles in a single operation from readily available starting materials. Isocyanide insertion into C═O double bonds is disclosed for the first time as indicated by the results of 18 O-labeling experiment. A mechanism for this domino reaction is proposed involving chemoselective heterodimerization of two different isocyanides, followed by indole-2,3-epoxide formation and rearrangement.

A tandem [3 + 2] cycloaddition/reductive cyclization of nitrochalcones with activated methylene isocyanides for the efficient synthesis of pyrrolo[2,3-b]quinolones is reported. In this reaction, the in situ generated dihydropyrroline acts as the internal reductant to convert the nitro into an electrophilic nitroso group, which undergoes subsequent C-N bond formation. Transition-metal-free, simple experimental procedure and ready accessibility of starting materials characterize the present transformation.

An unprecedented Rh(III)-catalyzed annulation of various benzamides and acrylamides with quinone monoacetals was developed for the facile and efficient one-pot synthesis of bridged nine-membered benzo[c]azonine-1,5(2H)-diones and 2-azabicyclo[4.3.1]dec-4-ene-3,8-diones. It is the first example of synthesis of nine-membered heterocycles through Rh(III)-catalyzed C-H bond functionalization, and both aryl and vinyl C-H bonds are tolerant in this reaction. A plausible mechanism is proposed on the basis of control experiments.

Push-pull alkenes, which bear electron-donating and -accepting group(s) at both termini of a C═C double bond, respectively, are of interest not only for their unique electronic properties but also for their importance as versatile building blocks in organic synthesis. In the world of ketene acetals having the push-pull alkene skeleton, ketene N,S-acetal is most likely the biggest family according to the number and types of these compounds. The first ketene N,S-acetal compound was reported in 1956. As a cyclic ketene N,S-acetal compound, nithiazine, the first lead structure of neonicotinoid insecticides, was reported in 1978. The characteristics of ketene N,S-acetals, which have the structural feature of ketene S,S-acetals and enaminones, make them versatile and easy to use, especially in cyclization and multicomponent reactions for the synthesis of various heterocyclic systems and related natural products. There has been an increasing wealth of information about the synthesis and synthetic applications of ketene N,S-acetals, especially, in recent years. This review provides comprehensive knowledge on the chemistry of ketene N,S-acetals.

The first formal [3+2] cycloaddition using α-trifluoromethyl-(indol-3-yl)methanols as the trifluoromethylated C3 1,3-dipoles for the construction of the five-membered carbocycle of 1-trifluoromethylated cyclopenta[b]indole alkaloids is described. An unprecedented step-wise dehydrative alkenylation of α-trifluoromethyl alcohols was revealed as the crucial transformation.