Dries De Vos

Nature Chemistry, Published online: 23 December 2021; doi:10.1038/s41557-021-00862-4

Nature Chemistry, Published online: 31 January 2022; doi:10.1038/s41557-021-00885-x

Tetramethylammonium iodide (TMAI)-promoted sulfenylation/annulation of enaminones using widely accessible thiosulfonates as the sulfenyl source was described under metal- and oxidant-free conditions. These methods provide an alternative and facile synthetic route to access a series of 3-sulfenylated chromones in moderate to good yields. This is a useful, time-efficient, and scalable procedure for the construction of C(sp²)−S bonds.

Abstract

A highly efficient and eco-friendly method for the tetramethylammonium iodide-mediated sulfenylation/annulation of enaminones using thiosulfonates as the sulfenyl source was described under open-air, metal-, and oxidant-free conditions. This method provides an alternative way of constructing C−S bonds, affords various substituted sulfenylated chromones in moderate to good yields, and shows broad substrate scope, and good functional group tolerance.

A visible-light-driven, metal-free catalyzed switchable chemo-selective transformation of aromatic aldehydes and ketones into pinacols and benzyl alcohols is reported.

Abstract

We report a versatile and efficient organophotoredox-catalyzed (4CzIPN) chemo-selective conversion of aromatic aldehydes and ketones into pinacols and benzyl alcohols. Hantzsch ester and thiophenol were used as the electron, proton and hydrogen atom donors. Product selectivity can be switched from pinacols to benzyl alcohols simply by adding a stoichiometric amount of thiophenol to the reaction system. The operationally simple protocol tolerates a variety of functional groups and selectively converts aromatic aldehyde into pinacol or benzyl alcohol in the presence of both aromatic ketone and aliphatic aldehyde.

Visible light-mediated radical cascade sulfonylation/cyclization reaction by employing iodine as catalyst without addition of any of photocatalyst and oxidant has been reported. Under the optimal reaction conditions, a series of sulfone-containing coumarin derivatives were obtained in moderate to good yields. Further, mechanistic investigations indicated that the reaction was started by visible light irradiation through iodine-catalyzed free radical cascade sulfonylation/cyclization pathway.

Abstract

We have presented a visible-light mediated, iodine catalyzed radical cascade sulfonylation/cyclization reaction by employing iodine as catalyst without addition of any of photocatalyst and oxidant. A number of sulfone-containing coumarin derivatives with different substituent and functional groups were obtained in moderate to good yields. Besides, the practicality and utility of this protocol were demonstrated by the scale up synthesis. Furthermore, mechanistic investigations including control experiments and light on/off studies indicated that visible-light irradiation and iodine catalyst were the essential elements to fulfill the radical cascade sulfonylation/cyclization process. This protocol featured green, economical and efficient, and opens a new opportunity for accessing to structurally diverse sulfone-containing coumarin derivatives.

Abstract

Selenols react with isocyanates under mild catalyst-free conditions to generate selenocarbamates in good yield and with high selectivity over potentially competing nucleophilic additions. The methodology enables the incorporation of a wide variety of functional groups providing access to a broad array of densely functionalised selenocarbamates. In the presence of competing heteroatom-centered nucleophiles, isocyanates selectively couple with selenols. Selenocarbamates exhibited thiol-peroxidase-like properties, enabling the reduction of hydrogen peroxide at the expense of thiols, which are converted into the corresponding disulfides. A series of control experiments suggested that the catalytic mechanism proceeds through a pathway, involving a H₂O₂-promoted transcarbamoylation reaction leading to a thiocarbamate with concomitant releasing of catalytically active selenolate anions. By undergoing peroxide-driven thiol-selenol exchange, selenocarbamates behave as equivalents of selenolate anions with thiol-peroxidase-like activity.

The anodic generation of symmetrical and unsymmetrical thiosulfonates is presented. The principle of the oxidation of symmetrical disulfides was expanded to the conversion of in situ generated unsymmetrical disulfides yielding the respective thiosulfonates. A strong dependency of the regioselectivity for the formation of the unsymmetrical thiosulfonates was encountered and allows their regioselective formation in the future.

Abstract

The anodic generation of symmetrical and unsymmetrical thiosulfonates is presented. First, the oxidation of disulfides yielding symmetrical thiosulfonates was realized. The direct synthesis is performed using a simple quasi-divided cell design, whereby using a supporting electrolyte is unnecessary. Its principle was then expanded to the conversion of unsymmetrical disulfides that were generated in situ through metathesis of two symmetrical disulfides. This enables a direct access to unsymmetrical thiosulfonates without any pre-functionalization or elaborate synthesis of the starting materials for the first time. The reaction scope was investigated by converting differently functionalized aliphatic and aromatic disulfides in moderate to very good yields. Furthermore, a sensitivity assessment for an improved reproducibility and a robustness screen to determine the compatibility of the reaction against functional groups were performed.