Enantioselective bifunctional iminophosphorane catalyzed sulfa-Michael addition of alkyl thiols to unactivated β-substituted-α,β-unsaturated esters

Abstract

The highly enantioselective sulfa-Michael addition of alkyl thiols to unactivated β-substituted-α,β-unsaturated esters catalyzed by a bifunctional iminophosphorane (BIMP) organocatalyst is described.

Fe(OTf)2‐CatalyzedThia‐Michael Addition Reaction: A Green Synthetic Approach to β‐Thioethers

“…Iron‐catalyzed asymmetric versions have disclosed high enantioselectivities of aromatic sulfoxides obtained by catalytic methods using H 2 O 2 as a green oxidant. [23c], Also, m ‐CPBA and Na 2 WO 4 /H 2 O 2 have been reported as efficient systems for the oxidation, in a separate step, of enantioenriched β‐thioethers to the respective sulfones without racemization. In this study, the oxidation step of β‐thioether 3a using the green Fe II /H 2 O 2 catalytic system was considered (Table ).…”

Enantioselective Synthesis of N−H‐Free 1,5‐Benzothiazepines

“…Even n-decanyl substituted pyrazolamide was found to be suitable (entry 6). b-Alkyl pyra-zolamides bearing three-, four-, five-, and six-membered rings, could be successfully utilized, providing the perfect results (99 %y ields and 89-96 % ee;e ntries [11][12][13][14]. Meanwhile, ethoxyl-and ester-substituted ones could also afford the corresponding products 3y and 3z in 92 and 65 %y ields with 80 and 91 % ee,r espectively (entries 9a nd 10).…”

Isothiourea-catalysed enantioselective Michael addition of N-heterocyclic pronucleophiles to α,β-unsaturated aryl esters

“…14 Despite these advances, only limited organocatalytic strategies have been developed that allow activation of a,b-unsaturated ester substrates, with the current state-of-the-art strategies having been showcased by List (silylium catalysis) 15 and Dixon (BIMP catalysis). 16 Chiral a,b-unsaturated acyl ammonium intermediates are readily prepared in situ from a,b-unsaturated acyl halides and anhydrides using tertiary amine Lewis base catalysts. 17 They have been utilised as convenient and powerful synthons in a number of organocascade reactions, 18 yet the Lewis base catalysed activation of a,b-unsaturated esters are rare.…”