Oxidative selenofunctionalization of allenes: convenient access to 2-(phenylselanyl)-but-2-enals and 4-oxo-3-(phenylselanyl)pent-2-enoates

Abstract

The controlled preparation of two types of α-seleno-α,β-unsaturated carbonyls, namely, α-selenoenals and α-selenoenones, have been accomplished.

A palladium-catalyzed approach to allenic aromatic ethers and first total synthesis of terricollene A

“…A gram-scale reaction between 1g and 2a delivered 1.0465 g of 3ga in 93% yield with a reduced loading of both the catalyst and ligand ( Scheme 2a ). As a class of synthetically useful chemicals, the versatile allenyl unit could be transferred into different structure units: selenohydroxylation and oxidation of 3ga with 1-fluoropyridinium/1,2-diphenyldiselane could deliver 2-selenoenal 4 with a Z / E selectivity of 94/6; 14 bromohydroxylation of this allenyl group in aqueous dioxane afforded terminal 2-bromoallylic alcohol 5 as the sole product in 72% yield; 15 the allenyl group may also be selectively transformed into the corresponding primary allylic alcohol 6 with an E / Z selectivity of 98/2 by a gold-catalyzed hydration reaction; 16 iodination of the allenyl group exclusively gave diiodide product ( Z )- 7 in 69% yield. 17 It should be noted that these products are difficult to synthesize through traditional transition-metal catalyzed coupling reactions.…”

Insights into the Recent Synthetic Advances of Organoselenium Compounds

“…As per mechanistic pathway proposed by the authors, the reaction of both the substrates mediates through phenylseleniranium intermediates produced by selective attack of electrophilic species PhSe(OTf) on the alkenes as per the substrate followed by the regioselective attack of water and then final oxidation by 1‐fluoropyridinium reagent [126] …”

“…Their enantioselectivity has been extended to conjugate addition of organometallic reagents to enones and palladiumcatalyzed stereoselective allylic alkylations. [34] In 2019, Benito et al, [126] reported regio and stereoselective organoselenium-mediated oxidative selenofunctionalization of allenes 60 to provide α-selenoenals 61 and α-selenoenones 62. The method utilizes the appealing reactivity of 1-Fluoropyridinium reagent towards oxidative functionalization reaction [16,127] and presence of water in the solvents used, plays a vital role in providing the carbaldehyde oxygen in 61 & 62 (Scheme 26).…”

“…As per mechanistic pathway proposed by the authors, the reaction of both the substrates mediates through phenylseleniranium intermediates produced by selective attack of electrophilic species PhSe(OTf) on the alkenes as per the substrate followed by the regioselective attack of water and then final oxidation by 1-fluoropyridinium reagent. [126] In 2020, Yang and Xia [128] reported visible-light photocatalyzed difunctionalization of alkene with diselenide which was mediated through photoexcitable Fe-amine complex (Scheme 27). This complex interacts with diselenides under the influence of blue LED light carried out in ethylacetate at room temperature to give the active selenium species.…”

Recent advances in tandem selenocyclization and tellurocyclization with alkenes and alkynes

“…In subsequent work, Alcaide and coworkers reported a metal-free oxidative selenofunctionalized reaction between allenes and diphenyl diselenide (Scheme 6). 14 Scheme 5 The selenocyclization of 2-indolinone-tethered allenols for the synthesis of spirocyclic selenolactams and quinoline-2,3-diones.…”