Amine‐ and Sulfonamide‐Promoted Wittig Olefination Reactions in Water

Abstract

Amine-promoted olefination: The reaction of a phosphonium salt and an aldehyde in water to yield alkenes with high E-configurational control is promoted by catalytic amounts of non-basic amines in aqueous bicarbonate media. Possible catalytic cycles involving imines and iminium intermediates are discussed.

Mild Chemical and Biological Synthesis of Donor–Acceptor Flanked Reporter Stilbenes: Demonstration of a Physiological Wittig Olefination Reaction

“…The olefination reaction could also be completed more rapidly in water by using the relatively stronger base potassium carbonate at 70 °C. Under these conditions, the reaction was complete within 3 h, yielding stilbene 3a in 76 % isolated yield as a 65:35 ( E )/( Z ) mixture, selectivity in accord with the literature data 16d. Full spectroscopic characterization of the ( E ) and ( Z ) isomers was accomplished, and the NMR spectroscopic data of the olefinic protons of each isomer are clearly resolved.…”

“…We have investigated aqueous Wittig olefination reactions over the last few years under increasingly milder chemical conditions showing that stabilized and semistabilized ylides can be efficiently generated and trapped to give a range of useful alkenes, including stilbenes 16. More recently, we demonstrated the first organocatalytic aqueous Wittig olefination reactions using weakly and non‐basic amines including L ‐proline, tosylamide, and diphenylamine 16d. We proposed a catalytic cycle for this process proceeding through an iminium ion intermediate16d as a carbonyl surrogate 17.…”

“…More recently, we demonstrated the first organocatalytic aqueous Wittig olefination reactions using weakly and non‐basic amines including L ‐proline, tosylamide, and diphenylamine 16d. We proposed a catalytic cycle for this process proceeding through an iminium ion intermediate16d as a carbonyl surrogate 17. To extend to even milder conditions, we decided to investigate the critical issue of whether a Wittig olefination process is compatible and achievable under physiological conditions.…”

Non-asymmetric organocatalysis

“…can be employed as the catalyst allowing the olefination of a range of electron-poor or electron-rich benzaldehyde derivatives 22 (Scheme 41). 84 Product isolation is simple. Upon reaction completion the mixture is cooled and the solid alkene 175 is isolated by suction filtration.…”

General Metal-Free Baeyer–Villiger-Type Synthesis of Vinyl Acetates

“…To study the stereoelectronic factors involved in our oxidation reaction a selection of α,β-unsaturated methylketones 1a – r , bearing diverse functional groups and substitution patterns, were reacted with an excess of Oxone under our finest reaction conditions (Table ). Ketones 1b – r were prepared in diastereopure form, ( E ), according to modified literature procedures . Although 2 equiv of Oxone sufficed to convert ketone 1a to vinyl acetate 3a (Table , entry 8), it was not the case for any other ketone 1b – r .…”