An Unusual Synthesis of N-Unsubstituted Benzazepinones

Synthetic exploration of electrophilic xanthylation via powerful N-xanthylphthalimides

Organic xanthates are broadly applied as synthetic intermediates and bioactive molecules in synthetic chemistry. Electrophilic xanthylation represents a promising approach but has rarely been explored mainly due to the lack of powerful electrophilic reagents. Herein, synthetic exploration of electrophilic xanthylation via powerful N-xanthylphthalimides was investigated. This strategy might provide a new avenue to less-concerned but meaningful electrophilic xanthylation in organic synthesis. With the help of these powerful reagents, electrophilic xanthylation of a wide range of substrates including aryl/alkenyl boronic acids, β-keto esters, 2-oxindole, and alkyl amines, as well as previously inaccessible phenols (first report) was achieved under mild reaction conditions. Notably, this simple electrophilic xanthylation of alkyl amine substrates will occur in the desulfuration reaction, consistent with the previously reported methods. Similarly, xanthamide and thioxanthate groups could also be transformed into desired nucleophiles via this electrophilic reagent strategy. The broad substrate scope, excellent functional group compatibility and late-stage functionalization of bioactive or functional molecules made them very attractive as general reagents which will allow rapid incorporation of SC(S)R (R = OEt, Oalkyl, NEt2 and SEt) into the target molecules.

Mandatory Sanitary Pass: Is it Justified?

Due to the emergency nature of the pandemic, many anti-COVID-19 vaccines were rushed ahead into testing through emergency-use authorization, leading to questionable accuracy of data with regard to the short and long-term efficacy and safety and time span of immune protection of these vaccines. Several scientifically founded concerns, along with many questions, have been raised with no clear answers as to whether these vaccines will have the same efficacy across different populations, among distinct regions, and for any emerging new variants. These concerns are coupled with the variable levels of preventive, therapeutic, and protective measures, such as the recent imposition of the sanitary pass in some but not all countries. Given the lack of a universal policy in its application, the recently reported short-lived vaccine-induced protective immunity of a few months duration, the consequent growing number of newly diagnosed COVID-19 cases in the most vaccinated countries, the equal spread of the Delta variant among vaccinated and unvaccinated individuals, the significantly lesser virulence of the Delta variant as reflected by the lower rate of hospitalization and death, and the recent admission by the US Centers of Disease Control and Prevention of the poor specificity of the COVID-19 polymerase chain reaction diagnostic panel in detection of SARS-CoV-2, this scientifically unfounded sanitary pass, based on recently emerging data from the most vaccinated countries, not only seems obsolete but can also be regarded as a tool of indirect coercion, forcing vaccination on those who may be vaccine prudent, therefore jeopardizing the essence of an individual's freedom of choice that is guaranteed by all international laws. In the presence of these concerns and many unanswered questions, it becomes evident that the informed consent rather than the sanitary pass should be enforced and should become not only a necessity but also mandatory.

Modular Approach to Substituted Pyridoazepinones

Pyridoazepinones are potentially interesting structures, yet they are still underexploited in the medicinal chemistry field and hard to obtain synthetically. We present a general and flexible synthetic route to substituted pyridoazepinones, enabled by the xanthate addition-transfer process, which furnishes the target molecules from readily available starting materials in generally good yields. The method shows good functional group tolerance and allows the preparation of pyridoazepinone scaffolds on gram scale.

A concise synthesis of cyclobrassinin and its analogues via a thiyl radical aromatic substitution

Cyclobrassinin and its six and seven-membered ring analogues have been synthesized through a thiyl radical-mediated intramolecular aromatic substitution of brassinin derivatives.

The Truce–Smiles rearrangement and related reactions: a review

The Truce–Smiles rearrangement is an X → C aryl migration reaction that is achieved by an intramolecular nucleophilic aromatic substitution pathway. The reaction exhibits a wide substrate scope with respect to a migrating aryl ring and leaving group, appearing in many different tandem reaction sequences, to achieve a wide variety of product outcomes. We present an extensive survey of reported examples of the Truce–Smiles rearrangement from the chemistry literature (1950s until present) organized by various substrate design variables or aspects of the reaction method. Present deficiencies in our understanding of the reaction are identified with recommendations for future research directions and useful developments in the application of the reaction are celebrated.

Some aspects of radical cascade and relay reactions

The ability to create carbon-carbon bonds is at the heart of organic synthesis. Radical processes are particularly apt at creating such bonds, especially in cascade or relay sequences where more than one bond is formed, allowing for a rapid assembly of complex structures. In the present brief overview, examples taken from the authors' laboratory will serve to illustrate the strategic impact of radical-based approaches on synthetic planning. Transformations involving nitrogen-centred radicals, electron transfer from metallic nickel and the reversible degenerative exchange of xanthates will be presented and discussed. The last method has proved to be a particularly powerful tool for the intermolecular creation of carbon-carbon bonds by radical additions even to unactivated alkenes. Various functional groups can be brought into the same molecule in a convergent manner and made to react together in order to further increase the structural complexity. One important benefit of this chemistry is the so-called RAFT/MADIX technology for the manufacture of block copolymers of almost any desired architecture.

Novel and facile synthesis of 1-benzazepines via copper-catalyzed oxidative C(sp3)–H/C(sp2)–H cross-coupling

A novel synthetic strategy for the facile construction of 1-benzazepines has been developedviacopper-catalyzed oxidative C(sp³)–H/C(sp²)–H cross-coupling.

The xanthate route to organofluorine derivatives. A brief account

The radical chemistry of xanthates allows numerous approaches to organofluorine compounds.

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration/fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3-dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles.

Radical cyclizations of cyclic ene sulfonamides occur with β-elimination of sulfonyl radicals to form polycyclic imines

Radical cyclizations of cyclic ene sulfonamides provide stable bicyclic and tricyclic aldimines and ketimines in good yields. Depending on the structure of the precursor, the cyclizations occur to provide fused and spirocyclic imines with five-, six-, and seven-membered rings. The initial radical cyclization produces an α-sulfonamidoyl radical that undergoes elimination to form the imine and a phenylsulfonyl radical. In a related method, 3,4-dihydroquinolines can also be produced by radical translocation reactions of N-(2-iodophenylsulfonyl)tetrahydroiso-quinolines. In either case, very stable sulfonamides are cleaved to form imines (rather than amines) under mild reductive conditions.