Chalcogenide MBH reaction

Indeed, the first example of other Lewis add, except for TiCU and BX3, catalyzed chalcogenide-MBH reactions dates back to the 1980s, when Noyori et al. first demonstrated that the conjugated addition of a silyl selenide to an enone catalyzed by TMSOTf provided a silyl enol ether, which can be successfully engaged in subsequent Mukaiyama retro-aldol reactions with various... 

Since the mechanism of chalcogenide-MBH reaction involved the Michael addition of chalcogenide to electron-deficient olefins and the intramolecular Michael addition reaction of a sulfide group to an enone moiety in an acidic medium is known, Kataoka et al. envisaged that the tandem Michael aldol... 

Scheme 7.24 MBH reaction with a,p-unsaturated thioesters catalyzed by chalcogenides...

Scheme 7.25 Reformulated mechanism for MBH reaction catalyzed by chalcogenides (Ch) in the presence of Lewis add...

A new tandem Michael-aldol reaction of a,ft-unsaturated compounds bearing a chalcogenide or thioamide group with electrophiles has been reviewed.163 The product o -(o -hydroxyalkyl)enones - Morita-Baylis-Hillman (MBH) adducts - can be formed with significant stereocontrol when an optically active thione is used. 

Several chalcogenide catalyzed MBH-type reactions are reported [146], Instead of the common ferf-amines or phosphanes, also higher organochalcogenides can act as nucleophilic activator. Such Morita-Baylis-Hillman reactions catalyzed by sub-stoichiometric amounts of sulfides and selenides in the presence of Lewis acid to activate the carbonyl group were described by Kataoka and co-workers [147, 148]. The reaction of p-nitrobenzaldehyde and 2-cyclohexenone has been used for screening a series of chalcogenide catalysts in dichloromethane at room temperature. The best result was found when 10 mol% of chalcogenide where employed with a stoichiometric amount of TiCl in the presence of excess 2-cyclohexenone as Michael acceptor (3 equiv., Table 7.10). 

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