1,3-Difunctionalization of Donor-Acceptor Cyclopropanes Enabled by Copper Nitrate: A Direct Approach to γ-Halonitrates

1,3-Difunctionalization of donor-acceptor cyclopropanes with copper nitrate and N-halosuccinimide was developed to efficiently afford γ-halonitrates. The pivotal factor of this protocol lies in the dual role of copper nitrate as a Lewis acid and an ideal nitrooxy source. The given approach features easy handling, good functional group compatibility, and wide substrate scope. Furthermore, various transformations of the obtained γ-chloronitrates underscore the remarkable synthetic potential inherent in this method.

Iodine-mediated decarboxylative coupling to synthesize β-sulfonyl-ene-amines/2,3-diarythio-pyrroles from α-amino acids and sodium sulfinates

A novel process has been developed for the selective synthesis of β-sulfonyl-enamines and 2,3-diarylthiopyrroles. This process utilizes the decarboxylative coupling and β-C(sp3)-H functionalization of α-amino acids. In this reaction, iodine functions dually as a tandem catalyst to initiate the decarboxylation of α-amino acids and as an oxidant to facilitate the formation of organic sulfides. This innovative approach not only simplifies the synthesis but also enhances the yield and selectivity of the desired products.

Synthesis of 4-functionalized pyrazoles via oxidative thio- or selenocyanation mediated by PhICl2 and NH4SCN/KSeCN

A series of 4-thio/seleno-cyanated pyrazoles was conveniently synthesized from 4-unsubstituted pyrazoles using NH4SCN/KSeCN as thio/selenocyanogen sources and PhICl2 as the hypervalent iodine oxidant. This metal-free approach was postulated to involve the in situ generation of reactive thio/selenocyanogen chloride (Cl-SCN/SeCN) from the reaction of PhICl2 and NH4SCN/KSeCN, followed by an electrophilic thio/selenocyanation of the pyrazole skeleton.

Electrochemical selective divergent C-H chalcogenocyanation of N-heterocyclic scaffolds

An electrochemical direct selective C-H chalcogenocyanation approach for indolizine derivatives under mild conditions has been described. Cyclic enone-fused, chromone-fused and 2-substituted indolizines possessing EDGs (electron donating groups) and EWGs (electron withdrawing groups) were successfully reacted with NH4SCN and KSeCN under electrochemical conditions to provide a wide array of mono and bis-chalcogenocyanate-indolizines in 75-94% yields. In addition, 1-substituted imidazo[1,5-a]quinolines were also successfully chalcogenocyanated under the optimized reaction conditions providing a platform for the synthesis of pharmaceutically privileged molecules. By switching the reaction conditions, the developed protocol offers selective synthesis of C-3 thiocyanate and 1,3 bis-thiocyanate indolizines in good to excellent yields under catalyst-free conditions. On the basis of control experiments and cyclic voltammetry data, a plausible reaction pathway is also presented.

NBS-Promoted Synthesis of Thiocyanated Aminomaleimides and Site-Selective Intramolecular Cyclization Access to 1,4-Benzothiazepines via S-CN Bond Cleavage

A transition metal-free concise and efficient protocol for the synthesis of thiocyanated aminomaleimides and benzo[e][1,4]thiazepine derivatives has been developed. The method involves an initial α-C-H thiocyanation of aminomaleimides with KSCN and TEMPO-mediated tandem S-CN bond cleavage/intramolecular cyclization substitution processes, which enables the formation of seven-membered S/N-heterocycles. This synthetic strategy provides a reliable method for the synthesis of biologically interesting benzo[e][1,4]thiazepine derivatives by using KSCN as sulfur sources as well as expands the application of enaminones thiocyanation reactions in heterocycles synthesis.

Thiocyanate promoted difunctionalization and cyclization of unsaturated C-C bonds to construct 1-sulfur-2-nitrogen-functionalized alkenes and 2-thiocyanate indolines

An unprecedented one-pot route to achieve highly regioselective 1-sulfur-functionalized 2-nitrogen-functionalized alkenes and 2-thiocyanate indolines from unsymmetrical ynamides (readily and generally available amides) using the commercially available inexpensive iodobenzene diacetate (PIDA) as the oxidant and potassium thiocyanate (KSCN) as the thiocyanate (SCN) source has been developed. The interconversion of thiocyanate (SCN) and isothiocyanate (NCS) groups simultaneously forms C-N and C-S bonds in this metal-free approach, while introducing important functional groups into homemade alkynes. A radical-chain mechanism, involving competing kinetically controlled chain transfer at the S atom and sterically-controlled chain transfer at the N atom of the thiocyanogen molecule in this mild approach, is proposed.

Oxidative thiocyanation of allylic alcohols: an easy access to allylic thiocyanates with K2S2O8 and NH4SCN

A practical method for the synthesis of allylic thioacyanates from allylic alcohols was disclosed employing K2S2O8 as the oxidant and NH4SCN as the thiocyanate source.

Expeditious Access to Spiro-Fused 2,5-Cyclohexadienones via Thio(seleno)cyanative ipso-Cyclization

A facile oxidative dearomatization of N-(p-methoxyaryl)propiolamides has been established for the synthesis of spiro-fused 2,5-cyclohexadienone frameworks via thio(seleno)cyanative ipso-cyclization in the presence of ceric ammonium nitrate (CAN) as the oxidant. The present method, involving the formation of C-S and C-C bonds, was also extended to (p-methoxyaryl)propiolates for thiocyanative ipso-cyclization. Furthermore, the obtained chalcogeno-spirocyclohexadienones were transformed into uniquely functionalized spirocyclohexadienone derivatives.

Synthesis of aromatic terminal allenes and aliphatic terminal alkynes from hydrazones using calcium carbide as an acetylene source

A simple method for the selective synthesis of aromatic terminal allenes and aliphatic terminal alkynes from the reactions of calcium carbide with ketone and aldehyde p-tosylhydrazones using copper as a mediator is described.

Electrophilic chloro(ω-alkoxy)lation of alkenes employing 1-chloro-1,2-benziodoxol-3-one: facile synthesis of β-chloroethers

A four-component reaction for electrophilic chloro(ω-alkoxy)lation of alkenes has been described. The stable chloro-iodine(iii) reagent and SOCl2 were used as electrophilic and nucleophilic chlorine sources, respectively. This approach provides a straightforward way to synthesize various useful β-chloro ω-chloroalkyl ethers from a wide range of alkenes, including electron-deficient, aromatic and unactivated alkenes. The synthetic applications of this approach were also explored in some useful transformations.

Metal-free difunctionalization of alkynes leading to alkenyl dithiocyanates and alkenyl diselenocyanates at room temperature

A simple and practical method for the synthesis of alkenyl dithiocyanates and alkenyl diselenocyanates has been developed via stereoselective difunctionalization of alkynes with NaSCN or KSeCN at room temperature. Through this methodology, a series of alkenyl dithiocyanates and alkenyl diselenocyanates could be efficiently and conveniently obtained in moderate to good yields under mild and metal-free conditions by the simple use of oxone and PhI(OAc)2 as the oxidants.

PIDA-mediated α-C–H functionalization of enaminones: the synthesis of thiocyano enaminones and chromones in water

Herein, an efficient, metal-free process for the α-C–H thiocyanation of enaminones was developed using PhI(OAc)₂ as an oxidant at room temperature in an aqueous medium.

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

Allyl and vinyl chlorides represent important structural motifs in organic chemistry. Herein is described the chemoselective and regioselective reaction of aryl- and α-substituted phenylallenes with the hypervalent iodine (HVI) reagent 1-chloro-1,2-benziodoxol-3-one. The reaction typically results in vicinal dichlorides, except with proton-containing α-alkyl substituents, which instead give chlorinated dienes as the major product. Experimental evidence suggests that a radical mechanism is involved.

Iodine-mediated regio- and stereoselective iodothiocyanation of alkynes in aqueous ethanol

Iodothiocyanation of alkynes with ammonium thiocyanate (NH₄SCN) and molecular iodine (I₂) has been described under transition-metal-free conditions in green aqueous ethanol. A series of β-iodo vinylthiocyanates were obtained from functional alkynes in good to excellent isolated yields. The synthetic protocol has the advantages of operational simplicity, broad substrate scope, good stereo-selectivity, the use of easily available starting materials.