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Please login to access the full content or check if you have access via Method 2: Syntheses of E-α,β-Unsaturated Ketones by Tandem Grignard/Wittig Alkenation Reactions of (Triphenylphosphoranylidene)ketene

DOI: 10.1055/sos-SD-027-00847

Schobert, R.; Gordon, G. J.Science of Synthesis, (2004271056.

(Triphenylphosphoranylidene)ketene 46 not only opens access to ester ylides (via addition of the respective alcohols to its Cα=Cβ bond), but also to acyl ylides by addition of carbon nucleophiles of the Grignard type. The metalated intermediates (possibly of the type 177) obtained upon heating mixtures of the cumulated ylide and pre-prepared Grignard solutions[‌25‌] are used immediately to alkenate carbonyl compounds to give E-2-enones 179, or can be first hydrolyzed to the corresponding acyl ylides 178, which are then subjected to Wittig alkenation in a separate step (Scheme 62). This is one of the few general approaches to highly functionalized and long-chain acyl ylides.[‌565‌] It is applied repeatedly as the key step in the syntheses of natural products such as the Queen's substance,[‌565‌] and pheromones of the peach fruit moth,[‌578‌] the Douglas fir tussock moth,[‌578‌] and the olive fly (Dacus oleae),[‌579‌] among others. Attempts to silylate or alkylate the metalated intermediates 177 have been, so far, unsuccessful.

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