Quest for Efficient Catalysts based on Zinc tert‐Butyl Peroxides for Asymmetric Epoxidation of Enones: C₂‐ vs C₁‐Symmetric Auxiliaries

Abstract

Zinc tert-butyl peroxide-based catalysts for the asymmetric epoxidation of enones using tert-butyl hydroperoxide as an oxidant have been developed. Ac omparative study of chiral monoanioninc N,N'-bidentate ligands, C 2 -symmetric bisoxazolinates and C 1 -symmetric enaminooxazolinates,r evealed excellent performance of C 1 -symmetric auxiliary ligands on catalytic asymmetric epoxidation of enones (up to 96% yield, 91% ee).

Reaching Milestones in the Oxygenation Chemistry of Magnesium Alkyls: towards Intimate States of O2 Activation and the First Monomeric Well‐Defined Magnesium Alkylperoxide

“…Moreover, we have also emphasized the essential role of the coordination state of the oxygenated organoaluminum and organozinc compounds, as well as the geometric requirements of an O 2 molecule approaching the metal centre . Apart from the fundamental aspects, these systematic studies have advanced rational design of metal alkyl/air systems as radical initiators for organic reactions, stoichiometric and catalytic asymmetric epoxidation of enones and pave the way to well‐defined metal alkoxides (not accessible through the classical alcoholysis path) as potential initiators of cyclic esters polymerization as well as to a new approach for the preparation of semiconductor zinc oxide quantum dots based on organozinc/air systems …”

“…Moreover,w eh ave also emphasizedt he essential role of the coordination state of the oxygenated organoaluminum [33,34] and organozinc [5,15,16,24] compounds, as well as the geometric requirementso fa nO 2 molecule approachingt he metal centre. [33,34] Apart from the fundamental aspects, these systematic studies have advanced rational designo fm etal alkyl/airs ystemsa sr adicali nitiators for organic reactions, [35][36][37] stoichiometric [38,39] and catalytic asymmetric epoxidation of enones [11,14,40] and pave the way to welldefined metal alkoxides (not accessible through the classical alcoholysis path) as potentiali nitiators of cyclic esters polymerization [25,41] as well as to an ew approach for the preparation of semiconductor zinc oxide quantum dots based on organozinc/ air systems. [42][43][44][45][46] Notably,t he oxygenationc hemistry of magnesium alkyls has remained anu ndeveloped area of research due to difficulties to control the respective reactions ystemsr esulting from the exceptionali nstability of MgOOR species.…”

An In‐Depth Look at the Reactivity of Non‐Redox‐Metal Alkylperoxides

“…Since Sharpless's groundbreaking discovery in the asymmetric epoxidation of the allylic alcohols mediated by TiOOR moieties, T MOOR‐type complexes have been extensively studied as intermediates in metal‐catalyzed oxidations of organic compounds . In turn, chemistry of NR M‐based alkylperoxides has flourished in recent years owing to their high catalytic activity in epoxidation of enones . Moreover, the latest discoveries demonstrated that oxygen‐centered radicals resulting from the O−O bond homolysis in NR MO−OR species are the key initiating species in radical organic reactions .…”

“…[3] In turn, chemistry of NR M-based alkylperoxides has flourished in recent years owing to their high catalytic activity in epoxidation of enones. [5,[18][19][20][21][22][23] Moreover,t he latest discoveries demonstrated that oxygen-centered radicals resulting from the O À Ob ond homolysis in NR MOÀOR species are the key initiating species in radical organic reactions. [24] Notably, NR MOOR systems have remained elusive since Franklandspioneering studies in 1849 (see below), and their isolation has proven challenging.…”

One Pot and Two Pot Synthetic Strategies and Biological Applications of Epoxy-Chalcones

“…Several other transitional metals catalysts have also been reported for efficient epoxidation reaction of chalcone derivatives. There are ethylperoxy zinc complex {[N{(C 3 F 7 )C(Cy)N} 2 ]Zn(μ-OOEt)} 2 (7) [110], zinc alkylperoxide/TBHP [111], zinc metal based tert-butyl peroxides (8) [112], chiral cobalt(III) complexes [113][114][115] [117], nickel Schiff base complex namely (Cr)NH 2 -MIL-101-PI-Ni (9) (Fig. 4) [118].…”