Science of Synthesis

Schobert, R.; Gordon, G. J., Science of Synthesis, (2004) 27, 1021.

Exploiting the inertness of dry finely powdered sodium amide[‌135‌,‌321‌,‌479‌] and potassium hydride[‌480‌] toward solid phosphonium salts, Schlosser has devised an “instant ylide” protocol in which the dry base and the phosphonium salt are mixed together and then stored for long periods. When required, the corresponding ylide is generated by dissolving the mixture in an aromatic or an ethereal solvent. Instant ylides can be applied on a microscale or in hundred kilogram quantities for industrial purposes. Mixtures of potassium hydride and alkyl(triphenyl)phosphonium salts, even those bearing base-sensitive functional groups such as fluoromethyl, chloromethyl, methylsulfanylmethyl, hydroxyalkyl, or picolyl, show “shelf half lives” (at 0°C) ranging from several months up to years.[‌480‌] Instant ylide mixtures of susceptible phosphonium salts and sodium amide coated with either paraffin wax or a polymer blend are also in use.[‌321‌] Various types of instant ylides are commercially available from the usual sources. Yields and stereoselectivities are virtually the same as for alkenations with lithium salt free ylides prepared according to the methods described in Section ‌27.24.2.2.4.1‌. A representative synthesis, that of (Z)-tetradec-6-en-1-ol (‌94‌), is shown in ‌Scheme 34‌.[‌321‌]

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References

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• 8.Meeeee-Meee, (8888) M 88-8, 8888.