Fujimoto-Belleau reaction

Treatment of enol lactone with Grignard reagent leads to cyclic a-substituted oc,P-unsaturated ketone. An alternative to the Robinson annulation. 

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L. A. Paquette, D. T. Belmont, Y.-L. Hsu, Journal of Organic Chemistry 1985, 50, 4667 Fujimoto-Belleau Reaction The Reaction ... 

Fujimoto-Belleau reaction. Synthesis of cyclic a-substituted a,(3-unsaturated ketones from enol lactones and Grignard reagents prepared from primary halides. 

Cyclic a, -ethyleneketones from enollactones Fujimoto-Belleau reaction... 

Other references related to the Fujimoto-Belleau reaction are cited in the literature. ... 

Beckwith (see Dowd-Beckwith Ring Expansion Reaction) Belleau (see Fujimoto-Belleau Reaction)... 

The mannose-derived lactone 40, produced by ozonolysis of the corresponding alkene, undergoes a modified Fujimoto-Belleau reaction yielding the vinyl phosphonate cyclohexenone 41.1 The epimeric lactone 43 however, yields the anticipated cyclcohexenone 42 (Scheme 12). Formation of 41 is rationalized by invoking hydroxide elimination from an enolate intermediate rather than the anticipated elimination of (MeO)2P(0)OH. 

Fujimoto-Belleau Reaction Nadia M. Ahmad 4.10.1 Description... 

The Fujimoto-Belleau reaction involves the formation of cyclic a-substituted a -unsaturated ketones from enols. 

The Fujimoto-Belleau reaction is a two-step one-pot transformation, which begins with a Grignard reaction (->1). This is followed by a hydrogen shift tautomerisation, (8—>9), an aldol reaction, (9 10), then loss of water through a reverse aldol (11 12) resulting in the final product. 

An example of different substrates amenable to transformation in the Fujimoto-Belleau reaction is shown by the treatment of benzazepine 15 with radioactively labeled methylmagnesium iodide. This was followed by quenching with water to afford diketone 17. In this two-step procedure the diketone was isolated in 80% yield, then treated with base to give the final a,) -unsaturated enone 18. The synthesis illustrates the utility of the Fujimoto-Belleau reaction in the production of radiolabelled 3-benzazepines using labelled methyl iodide. 

In their studies on mannose-derived carbocyclic sugars, Trabsa and co-workers applied a Wadsworth-Emmons modification of the Fujimoto-Belleau reaction to give a vinyl phosphonate rather than the expected enone. Originally this procedure was used as an alternative to the Ferrier cyclisation, which requires acidic conditions. However, the authors found that the formation of an enone or vinyl phosphonate depended on the carbohydrate stereochemistry. Lactone 21 gave the vinyl phosphonate 22 when treated... 

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