A Simple Zinc-Mediated Method for Selenium Addition to Michael Acceptors

Abstract

In this work, we focused our attention on seleno-Michael type reactions. These were performed using zinc-selenolates generated in situ from diphenyl diselenide 1, 1,2-bis(3-phenylpropyl)diselenide 30, and protected selenocystine 31 via an efficient biphasic Zn/HCl-based reducing system. Alkenes with a variety of electron-withdrawing groups were investigated in order to gauge the scope and limitations of the process. Results demonstrated that the addition to acyclic α,β-unsaturated ketones, aldehydes, esters amides, and acids was effectively achieved and that alkyl substituents at the reactive β-centre can be accommodated. Similarly, cyclic enones undergo efficient Se-addition and the corresponding adducts were isolated in moderate to good yield. Vinyl sulfones, α,β-unsaturated nitriles, and chalcones are not compatible with these reaction conditions. A recycling experiment demonstrated that the unreacted Zn/HCl reducing system can be effectively reused for seven reaction cycles (91% conversion yield at the 7° recycling rounds).

Polyselenide-Catalyzed Cyclohexene Oxidation to Produce 1,2-Cyclohexanediol

“…[24] The investigations of smart techniques involving selenium and oxidation reactions with molecular oxygen are booming in recent years. [25] 4 Experimental section 4.1 General methods Infrared (IR) spectra were determined on a Bruker Tensor 27 IR spectrometer. Liquid-state NMR spectra were recorded on a Bruker Avance III 400 nuclear magnetic resonance spectrometer (400 MHz for 1 H NMR spectroscopy and 100 MHz for 13 C NMR spectroscopy) by using CDCl 3 as the solvent and Me 4 Si as the internal standard.…”

Simple Zn-Mediated Seleno- and Thio-Functionalization of Steroids at C-1 Position

“…h for 15 min in the zinc-containing, biphasic acidic system [20]. Then, organic and aqueous layers were transferred under argon into a flask containing 1,4-androstadiene-3,17-dione (1) or prednisone acetate (2), and the resulting mixture was stirred for an additional 3 h at room temperature.…”

Strategies for the Synthesis of Selenocysteine Derivatives

“…Davis and co-workers 59 also explored the Se-Michael addition to a nonchiral Dha (methyl 2-acetamidoacrylate, 105) with different allylselenolate nucleophiles to obtain in good yields the corresponding racemic protected ASec derivative 106 (Scheme 29). On the other hand, Santi and co-workers 60 recently published some Se-Michael type reactions on several acyclic and cyclic enones with zinc-selenolates generated "in situ" from N-Bocprotected selenocystine methyl ester 11 via a biphasic Zn/HClbased reducing system to achieve β-seleno-α-amino acid derivatives 107 using disconnection "b", but with low yields and diastereoselectivities (Scheme 29). Because of this lack of chiral Se-Michael reactions, Peregrina and co-workers 61 not only carried out the synthesis of α-D-GalNAc-L-Sec by using the Se-nucleophilic 1,4-attack to the chiral Dha 108 (previously exploited in the S-and N-Michael additions), but also extended this novel synthetic methodology to the synthesis of other important β-seleno-α-amino acids in enantiomerically pure forms 110 (PhSec ASec, SeLys and SeLan).…”

“…105) with different allylselenolate nucleophiles to obtain in good yields the corresponding racemic protected ASec derivative 106 (Scheme 29). On the other hand, in 2020 Santi and co-workers 60 published some Se-Michael-type reactions on several acyclic and cyclic enones with zinc selenolates generated in situ from N-Boc-protected selenocystine methyl ester 11 via a biphasic Zn/HCl-based reducing system to achieve -seleno--amino acid derivatives 107 using disconnection 'b', but with low yields and diastereoselectivities (Scheme 29).…”