Dries De Vos

A palladium photocatalytic method is reported for the successful synthesis of primary anilines by the cross-coupling of aryl halides and sodium azide under open-air conditions at room temperature. For the first time, diverse divalent palladium complexes are shown to undergo photoexcitation to give carbon-nitrogen (C−N) cross-coupled product under air without using sophisticated ligands.

Abstract

The development of metal complexes that function as both photocatalyst and cross-coupling catalyst remains a challenging research topic. So far, progress has been shown in palladium(0) excited-state transition metal catalysis for the construction of carbon-carbon bonds where the oxidative addition of alkyl/aryl halides to zero-valent palladium (Pd⁰) is achievable at room temperature. In contrast, the analogous process with divalent palladium (Pd^II) is uphill and endothermic. For the first time, we report that divalent palladium can act as a light-absorbing species that undergoes double excitation to realize carbon-nitrogen (C−N) cross-couplings under air. Differently substituted aryl halides can be applied in the mild, and selective cross-coupling amination using palladium acetate as both photocatalyst and cross-coupling catalyst at room temperature. Density functional theory studies supported by mechanistic investigations provide insight into the reaction mechanism.

Julia-Kocienski olefination has been lately often used in the preparation of trisubstituted alkenes which serve as precursors of natural products and their analogs as well of pharmaceutically interesting/biologically important compounds. Significant observations regarding the stereoselectivity of those reactions are described in this reviewing work covering comprehensively the period 2016–2022.

Abstract

Julia-Kocienski olefination, a coupling reaction between a carbonyl component and a sulfone partner, has emerged as a powerful synthetic tool in the preparation of several organic compounds. A number of interesting examples involving particularly the preparation of trisubstituted alkenes along with important observations regarding the stereoselectivity of those reactions have been recently reported. This reviewing work covers the literature for the period 2016–2022 and describes in a comprehensive way the progress and developments of Julia-Kocienski olefination application in the synthesis of trisubstituted alkenes which serve as precursors of natural products and their analogs as well of pharmaceutically interesting/biologically important compounds. Moreover, key methodology results dealing with the investigation of the optimum conditions and stereoselectivities and new modifications and approaches are discussed.

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.

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.