Synthesis of 3,3-Disubstituted Allyl Isoindolinones via Pd-Catalyzed Decarboxylative Allylic Alkylation

Herein, we report a mild palladium-catalyzed decarboxylative allylic alkylation of allyl ester-substituted isoindolinone substrates to afford a variety of 3,3-disubstituted isoindolinone derivatives. The decarboxylative coupling reaction tolerates a range of functional groups, including ketones and alkenyl halides, and does not require protection of the isoindolinone nitrogen. Additionally, the reaction was found to proceed in near-quantitative yield for most substrates evaluated. Based on the isolation of competing cyclopropane and protonation products, a reaction mechanism is proposed.

Recent Advances in the Transition Metal-Free Synthesis of Heterocycles from α, β-Unsaturated Ketones

Heterocyclic compounds are an inevitable part of our life. These important classes of molecules have a wide range of applications starting from life-sustaining drugs to agrochemicals. Numerous methods, including metal...

Acyclic Twisted Amides

In this contribution, we provide a comprehensive overview of acyclic twisted amides, covering the literature since 1993 (the year of the first recognized report on acyclic twisted amides) through June 2020. The review focuses on classes of acyclic twisted amides and their key structural properties, such as amide bond twist and nitrogen pyramidalization, which are primarily responsible for disrupting nN to π*C═O conjugation. Through discussing acyclic twisted amides in comparison with the classic bridged lactams and conformationally restricted cyclic fused amides, the reader is provided with an overview of amidic distortion that results in novel conformational features of acyclic amides that can be exploited in various fields of chemistry ranging from organic synthesis and polymers to biochemistry and structural chemistry and the current position of acyclic twisted amides in modern chemistry.

Diastereoselective trifunctionalization of pyridinium salts to access structurally crowded azaheteropolycycles

A highly diastereoselective dearomative trifunctionalization of pyridinium salts with multifunctional o-hydroxyl aromatic azomethine ylides has been established, which not only provided a convenient and rapid method to assemble challenging and architecturally crowded chroman-pyrrolidine-hydrogenated pyridine fused pentacycles, but also represented a rare successful example of the higher-order multifunctionalization of pyridiniums.

Construction of bridged polycycles through dearomatization strategies

Bridged polycycles are privileged molecular skeletons with wide occurrence in bioactive natural products and pharmaceuticals. Therefore, they have been the pursing target molecules of numerous chemists. The rapid and convenient generation of sp3-rich complex three-dimensional molecular skeletons from simple and easily available aromatics has made dearomatization a highly valuable synthetic tool for the construction of rigid and challenging bridged rings. This review summarizes the-state-of-the-art advances of dearomatization strategies in the application of bridged ring formation, discusses their advantages and limitations and the in-depth mechanism, and highlights their synthetic value in the total synthesis of natural products. We wish this review will provide an important reference for medicinal and synthetic chemists and will inspire further development in this intriguing research area.

Assembly of functionalized π-extended indolizine polycycles through dearomative [3+2] cycloaddition/oxidative decarbonylation

Reported herein is an unexpected construction of functionalized π-extended indolizine polycycles through a one-pot two-step cascade process comprising the base-promoted dearomative [3+2] cycloaddition of quinilinium salts and 3-alkenyl oxindoles, followed by a DDQ-mediated oxidative decarbonylation. Moreover, we could achieve the substrate-controlled diverse synthesis of structurally strained cyclopropane spirooxindole by using pyridinium salts as starting materials.

Diastereoselective construction of cage-like and bridged azaheterocycles through dearomative maximization of the reactive sites of azaarenes

A highly diastereoselective multicomponent dearomative multifunctionalization of N-alkyl activated azaarenes with 1,5-diazapentadienium salts has been developed to access structurally rigid and synthetically challenging cage-like and bridged azaheterocycles.

Rapid construction of cyclopenta[b]naphthalene frameworks from propargylic alcohol tethered methylenecyclopropanes

We have developed a new synthetic methodology for the rapid construction of cyclopenta[b]naphthalene frameworks from the reaction of propargylic alcohol tethered methylenecyclopropanes with mesyl chloride in the presence of triethylamine through cascade cyclization. The reaction can be performed under mild conditions without the use of transition metals, affording the target products in moderate to good yields, and this cyclization reaction process can be scaled up to a gram-scale synthesis.

Chalcone-Based Pyridinium Salts and Their Diastereoselective Dearomatization To Access Bibridged Benzoazepines

New chalcone-based pyridinium salts have been successfully exploited, which could smoothly participate in the highly diastereoselective dearomatization with binucleophilic enaminones by taking advantage of their multiple reactive sites to construct bibridged benzoazepines in up to 89% yields. The key to the success was the skillful and unprecedented C-3 functionalization of the new pyridinium salts. This work not only provides a kind of novel pyridinium salt synthon but also achieves the first C-3 functionalization of pyridinium salts to construct complex and challenging bibridged benzoazepines with high synthetic efficiency.

A synthetic route to 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyranoindoles via ring-opening/Pictet–Spengler reaction of aziridines and epoxides with indoles/aldehydes

A route to 1,4-disubstituted tetrahydro-β-carbolines and tetrahydropyrano[3,4-b]indoles in high yields and stereoselectivity via S_N2-type ring opening/Pictet–Spengler reaction of aziridines and epoxides with indoles is described.

Regio- and diastereoselective dearomatizations of N-alkyl activated azaarenes: the maximization of the reactive sites

An unprecedented base-promoted multi-component one-pot dearomatization of N-alkyl activated azaarenes was developed, which enabled the synthesis of complex and diverse bridged cyclic polycycles with multiple stereocenters in a highly regio- and diastereoselective manner. Besides, we realized the step-controlled dearomative bi- and trifunctionalization of quinolinium salts. These transformations not only achieved the maximization of the reaction sites of pyridinium, quinolinium and isoquinolinium salts to enhance structural complexity and diversity, but also opened up a new reaction mode of these N-activated azaarenes. A unique feature of this strategy is the use of easily accessible and bench-stable N-alkyl activated azaarenes to provide maximum reactive sites for dearomative cascade cyclizations. In addition, the salient characteristics including high synthetic efficiency, short reaction time, mild conditions and simple operation made this strategy particularly attractive.

An unprecedented base-promoted multi-component one-pot dearomatization of N-alkyl activated azaarenes was developed to construct complex and diverse bridged cyclic polycycles with multiple stereocenters in a highly regio- and diastereoselective manner.

Diastereoselective Construction of 2-Aminoindanones via an In(OTf)3-Catalyzed Domino Reaction

An In(OTf)₃-catalyzed domino reaction involving sequential oxidative ring opening of aziridines by using the solvent dimethyl sulfoxide and intramolecular Michael addition has been developed for the modular synthesis of 2-aminoindanone compounds by the formation of one new C═O bond and one new C-C bond. The notable feature of this strategy includes broad substrate scope, excellent trans-diastereoselectivities, highly functionalized products, and mild conditions. The catalyst In(OTf)₃ plays an important role in the formation of the indanone ring.

Synthesis and Organocatalytic Asymmetric Nitro-aldol Initiated Cascade Reactions of 2-Acylbenzonitriles Leading to 3,3-Disubstituted Isoindolinones

In this work, we investigated two strategies for the synthesis of the challenging ketones 2-acylbenzonitriles and we report their use as electrophiles in asymmetric organocatalytic cascade reactions with nitromethane. Promising results were obtained in the presence of chiral bifunctional ammonium salts under phase transfer conditions, which led to novel 3,3-disubstituted isoindolinones in quantitative yields and moderate enantioselectivity.

An unexpected cascade reaction of 3-hydroxyoxindoles with coumarin-3-carboxylates to construct 2,3-dihydrobenzofuran spirooxindoles

An unexpected Michael addition-inspired ring-opening/closure cascade reaction of 3-hydroxyoxindoles with coumarin-3-carboxylates was developed.