Domino hydroformylation-Wittig

In a similar way, carbocycles having a quaternary center could be obtained from acyclic unsaturated 1,3-dicarbonyl compounds [206]. Other combinations are the domino hydroformylation/Wittig olefmation/hydrogenation described by Breit and coworkers [207]. The same group also developed the useful domino hydroformyla-tion/Knoevenagel/hydrogenation/decarboxylation process (Scheme 6/2.14) [208] a typical example is the reaction of 6/2-66 in the presence of a monoester of malonic acid to give 6/2-67 in 41 % yield in a syn anti-ratio of 96 4. Compounds 6/2-68 and 6/2-69 can be assumed as intermediates. 

For domino hydroformylation/Wittig olefinations see a) B. Beeit, S. K. Zahn, Angew. Chem. 1999, 111, 1022-1024 Angew. Chem. Int. Ed. Engl. 

Scheme IS. Domino hydroformylation-Wittig olefination. Reagents and conditions 1.1 Equiv.

Rhodium-catalyzed hydroformylation of terminal alkenes in the presence of stabilized phosphorus yhdes was found to initiate a domino hydroformylation-Wittig olefination process. When monosuhstituted acceptor-stabilized phosphorus ylides were employed, a hydrogenation step follows the Wittig olefination to give a domino hydroformylation-Wittig olefination hydrogenation process (Equation 7.19) [166]. 

A reaction in agreement with these efficiency criteria would be a domino stereoselective-hydroformylation-Wittig olefination process. This would require that the hydroformylation reaction be compatible with the presence of a Wittig ylid throughout the course of the reaction. 

Wittig yhdes have been shown to be compatible with hydroformylation conditions, and may thus be used in a domino reaction sequence such as from 16a to 38 (Scheme 5.15) [20]. When an a-unsubstituted ylide is employed, the resulting alkene undergoes in-situ rhodium-catalyzed hydrogenation in a triple tandem reaction to convert 10 a to 39. Several other examples were reported establishing the generality of this domino reaction sequence. 

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