The ring-opening of cyclic sulfamidates and sulfates with α-fluorocarbanion generated from fluorobis(phenylsulfonyl)methane (FBSM) and subsequent reductive desulfonylation have been developed. This fluoromethylation approach allows access to γ- and δ-fluoroamines as well as γ- and δ-fluoroalcohols in high yields. The monofluoromethylation of cyclic sulfamidates with α-fluorocarbanion of ethyl 2-fluoroacetoacetate was also described.

Abstract

A regioselective fluoromethylation by ring-opening of cyclic sulfamidates and sulfates with α-fluorocarbanions and subsequent reductive desulfonylation is developed. Fluorobis(phenylsulfonyl)methane (FBSM) was explored as fluoromethide equivalent and the reaction was extended to the α-fluorocarbanion of ethyl 2-fluoroacetoacetate. This approach allows access to γ- and δ-fluoroamines as well as γ- and δ-fluoroalcohols in high yields.

The synthesis of phenanthridinones and carbazoles by intramolecular photo- and Base-promoted Homolityc Aromatic Substitution photo-BHAS) reaction from N-(2-halobenzyl)-N-methylanilines or N-substituted-N-phenyl anilines is presented. The synthetic protocol uses only KO ^t Bu and DMSO to generate aryl radicals under visible-light irradiation. An exciplex complex between the substrates and the dimsyl anion could be involved in the initiation step.

Abstract

A visible-light-driven approach towards phenanthridin-6(5H)-one and carbazole rings synthesis under transition-metal-free conditions is here reported. Phenanthridinones and carbazoles are synthesized through an intramolecular arylation of the corresponding N-(2-halobenzyl)-N-methylanilines or N-substituted-N-phenyl anilines using KO ^t Bu as base in dimethyl sulfoxide (DMSO) at room temperature (rt), employing blue light emitting diodes (LEDs) as the light source. The reaction proceeds through photo- and base-promoted homolytic aromatic substitution via photoinduced electron transfer mechanism and it exhibits good tolerance to different functional groups, resulting in good to very good yields (up to 86 %).

The Front Cover celebrates the combination of photoredox catalysis with titanium catalysis and all the exciting and stimulating transformations that can be achieved without the use of metal reductants. In the present report, the combination of an organophotocatalyst with a catalytic amount of titanocene dichloride gave access to a library of differently functionalized α-vinyl-β-hydroxy esters through an α-selective vinylogous Reformatsky approach emploiyng the Hantzsch’ ester as stoichiometric organic reductant. More information can be found in the Research Article by P. G. Cozzi, F. Calogero et al.

This review provides an overview of recent advances in direct C−H trifluoromethylselenolation and fluoroalkylselenolation from development to the application of corresponding reagents.

Abstract

Due to their high lipophilicity and strong electron-withdrawing property, more and more attention has been paid to introducing trifluoromethylseleno and fluoroalkylseleno moieties into organic molecules. In this short review, we categorize the synthesis of compounds that combine selenium and fluorinated moieties into two main types: trifluoromethylselenolation (CF₃Se) and fluoroalkylselenolation (R_fSe, except CF₃Se). This review aims to provide a summary of the recent advances in direct C−H trifluoromethylselenolation and fluoroalkylselenolation from the synthesis of trifluoromethylselenolation and fluoroalkylselenolation reagents to their application. Based on the method of how the R_fSe group was introduced, the main content is divided into three parts: transition-metal-free reactions, transition-metal-mediated/catalyzed reactions and photo-catalyzed reactions. The general substrate scope, mechanism and limitations would also be discussed so that we hope the review will serve as an inspiration for further research in this appealing research field.

A novel dual visible-light-photoredox- and titanocene-catalyzed protocol for the highly regioselective access to α-vinyl, β-hydroxy esters is reported. Thanks to a comprehensive investigation on the reaction conditions, the disclosure of an original protocol based on the Barbier-type properties of titanocene complexes in low oxidation state is achieved. The reaction showed very good compatibility with several functional groups and a detailed photophysical studies highlighted the role played by each component of the reaction.

Abstract

For the first time, a dual photoredox- and titanocene-catalyzed methodology for the regioselective access to α-vinyl-β-hydroxy esters towards aldehyde allylation with 4-bromobut-2-enoate is reported. The protocol is based on the Barbier-type properties of the inexpensive and available Cp₂TiCl₂ in catalytic amount (5 mol%). The developed mild reaction conditions gave access to a library of differently functionalized α-vinyl-β-hydroxy esters in moderate diastereoselectivity, employing the commercially available ethyl 4-bromobut-2-enoate and both aromatic and aliphatic aldehydes. The reaction was realized under visible light irradiation, in the presence of an organophotocatalyst (3DPAFIPN, 2 mol%) combined with Hantzsch's ester as the sacrificial reductant. In contrast to other Barbier-type reactions employing ethyl 4-bromobut-2-enoate, the photoredox system ensures a better regioselectivity. Moreover, the use of preformed organometallic nucleophilic species (e. g., dienolborinates), and the need of metal reductants or stoichiometric amount of transition metals in low oxidation state for Barbier-type reactions, is avoided. To support the experimental evidence, a detailed photophysical study shed light on the mechanism of the reaction.

Undivided electrochemical cells were utilized for sulphenylation reactions to prepare sulphur-containing naphthoquinones with potent bioactivity.

Abstract

Undivided electrochemical cells enable economical preparation of sulphur-containing naphthoquinones through electrochemical sulphenylation of quinoidal compounds. The environmentally friendly and efficient protocol eliminates the use of chemical oxidants and facilitates the synthesis of the desired molecules. This approach offers an efficient and versatile method to synthesize quinones that exhibit cytotoxicity against cancer cell lines.

In this work, a mild and straightforward access to various substituted naphthalene-fused oxepines from readily available Donor-Acceptor (D-A) cyclobutanes and 2-naphthols is reported. A broad range of functional groups is tolerated during this transformation.

Abstract

A mild and straightforward access to various substituted naphthalene-fused oxepines from readily available Donor-Acceptor (D-A) cyclobutanes is reported. This method involves the Lewis acid-catalyzed reactions of D-A cyclobutanes with 2-naphthols to afford ring-opened products, which can undergo intramolecular cyclization mediated by the NBS-base system to yield corresponding naphthalene-fused oxepines. The cyclization protocol involves a nucleophilic attack of the oxygen of 2-naphthol on the newly formed electrophilic acceptor end of D-A cyclobutane.

A simple and effective method for the synthesis of 9-sulfenylphenanthrenes was developed. The reaction proceeds through BF₃ ⋅ OEt₂-mediated annulation of 2-alkynyl biaryls with N-arylthio succinimides at room temperature. With this method, a series of 9-sulfenylphenanthrenes was efficiently obtained in good to excellent yields under mild and metal-free conditions.

Abstract

A simple and effective method for the synthesis of 9-sulfenylphenanthrenes was developed via BF₃ ⋅ OEt₂-mediated annulation of 2-alkynyl biaryls with N-arylthio succinimides at room temperature. Through this methodology, a series of 9-sulfenylphenanthrenes could be efficiently and conveniently obtained in good to excellent yields under mild and metal-free conditions.

Trichloromethylative olefin lactonization was reported. A photoredox iridium catalyst irradiated with blue LEDs promoted the reaction without using hazardous reagents. The mechanistic studies were performed by experimental and theoretical means. The trichloromethyl moiety of the product could be converted to the corresponding dichloroalkene and chloroalkyne in addition to the carboxyl group.

Abstract

A trichloromethylative olefin lactonization reaction using an iridium photoredox catalyst was developed. The reactions proceeded at room temperature for olefins with various substituents and substitution patterns, and a variety of lactones with a tetrasubstituted carbon and trichloromethyl group were obtained regio- and stereoselectively. The reaction mechanism was elucidated through isotope labeling experiments. The chemical properties of the lactones containing the trichloromethyl groups were investigated, and synthetic transformations of the product were realized.

Pd-catalyzed [3+2] annulations go dehydrogenative: a new protocol enables the Pd(II)-catalyzed [3+2] annulation between resonance-stabilized acetamides (or 3-oxoglutarates) and β,γ-unsaturated cyclic carbonyl derivatives. This dehydrogenative strategy represents a more atom- and step- economical version than the corresponding Pd(0)-catalyzed redox-neutral couplings previously studied by our group, enabling the straightforward construction of a number of heteropolycyclic structures.

Abstract

The significance of cross dehydrogenative couplings has increased considerably in recent years. This article revisits the [3+2] C−C/N−C, C−C/O−C and C−C/C−C annulation strategy, recently reported by our group, according to a Pd(II) catalyzed dehydrogenative variant. Our original report relied on Pd(0) catalysis, using α,β-unsaturated-γ-oxy carbonyls as bis-electrophiles and resonance-stabilized acetamides or 3-oxoglutarates as C/N and O/C or C/C bis-nucleophiles, respectively. In this more modern and straightforward Pd(II)-catalyzed dehydrogenative approach, β,γ-unsaturated carbonyl derivatives replace α,β-unsaturated-γ-oxy carbonyls as bis-electrophiles. Our study includes experimental optimization and showcases the synthetic versatility in the formation of diverse heterocyclic structures, such as bicyclic lactams, furo-cycloalkanones and bicycloalkane-diones. Furthermore, a mechanism is proposed to elucidate the underlying processes involved in these reactions.