Asymmetric vinylogous Michael reaction of cyclic enones with silyloxy furans

Abstract

The asymmetric vinylogous Michael reaction of cyclohexenone/medium and large cyclic enones with 2-silyloxyfuran is still a synthetic challenge. In this report, we have explored 1,4-conjugate addition of an enantioselective chiral, primary diamine catalyzed, 2-silyloxy furan to various cyclic enones and β-substituted cyclic enones. The reaction provided syn-Michael adducts (cycloalkane connected γ-butenolide) with good yields, diastereo and enantioselectivities. Furthermore, the synthetic potential of these syn-Michael adducts is demonstrated by 1,4-addition of nucleophiles on the butenolide substructure.

Silyldienolates in Organocatalytic Enantioselective Vinylogous Mukaiyama-Type Reactions: A Review

“…Almost 10 years later, a series of related articles were published [65][66][67]. The groups of Pápai and Pihko focused on the challenging stereocontrol of a VMMcR with α-substituted enals [65].…”

“…The corresponding products 92 were obtained in high yields (up to 97%) and with exceptional enantiomeric excesses (>99% ee). Almost 10 years later, a series of related articles were published [65][66][67]. The groups of Pápai and Pihko focused on the challenging stereocontrol of a VMMcR with α-substituted enals [65].…”

Stereoselective Synthesis of Spiro-α-methylene-γ-lactams via Chiral Quaternary 3-Aminooxindole Adducts Accessed by Zn-Mediated Allylation of Sulfinyl Ketimines

“…The reaction was performed by following a reported procedure. 22 To a solution of compound 5c (53 mg, 0.1 mmol) in anhydrous nitromethane (0.332 mL, 6.2 mmol, 62 equiv) was added DBU (0.02 mmol, 03 L, 0.2 equiv) and the reaction mixture was stirred at r.t. for 16 h. The solvent was evaporated off under reduced pressure. The anti/syn ratio (99:1) was determined by 1 H NMR analysis of the crude product ( major: 3.77 ppm) and the crude mixture was purified by flash chromatography on silica gel to give the product 6d.…”

Recent Developments in Enantioselective Organocatalytic Michael Reactions in Aqueous Media

“…So far, only few organocatalytic enantioselective additions of C-nucleophiles to hindered , '-disubstituted Michael acceptors have been successfully developed [36]. In this context, Singh et al have investigated the enantioselective vinylogous Michael reaction of 2-siloxyfurans with cyclic , -unsaturated ketones in the presence of (R,R)-diphenylethylenediamine 14 (scheme 21) as organocatalyst [47]. An acid additive, such as trichloroacetic acid, was needed to achieve good results.…”