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Please login to access the full content or check if you have access via Variation 2: (Triphenylphosphoranylidene)ketene Acetals by O-Alkylation/Deprotonation

DOI: 10.1055/sos-SD-027-00847

Schobert, R.; Gordon, G. J.Science of Synthesis, (2004271047.

Ester ylides, formylated ylides, and dithioester ylides are readily O- or S-alkylated, respectively. The corresponding cumulated ylides can be easily prepared by α-deprotonation of the resulting vinylphosphonium salts with strong bases such as sodium amide in liquid ammonia. (Diethoxyvinylidene)triphenylphosphorane (148) may thus be obtained from the phosphonium tetrafluoroborate 147, which in turn is made by alkylating (ethoxycarbonylmethylene)triphenylphosphorane[‌300‌] with the Meerwein salt triethyloxonium tetrafluoroborate (Scheme 53).[‌186‌] A C-alkylated byproduct from this reaction must be removed by conversion into the corresponding ylide and extraction with aqueous sodium hydroxide/benzene. Likewise, the sulfur congener 150 is accessible by deprotonation of the phosphonium bromide 149, which itself is obtained by exclusive S-alkylation of (ethyldithiocarbonylmethylene)triphenylphosphorane[‌566‌] with the softer reagent ethyl bromide.[‌51‌] Analogously, (triphenylphosphoranylidene)acetaldehyde[‌187‌] is alkylated with ethyl bromide to give the phosphonium salt 151, deprotonation of which with sodium amide in liquid ammonia gives the ylide 152 as a highly air-sensitive crystalline solid; the formation of this compound opens access to Z-α,β-unsaturated aldehydes.[‌567‌]

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(8-Meeeeeeeeeeeeeee)eeeeeeeeeeeeeeeeeeee (888) eeee (Meeeeeeeeeeeeeeeeeeeeeeeee)eeeeeeeeeeee; Meeeeee Meeeeeeee:[‌888‌]

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Meeeee 8-Meeeee-8-(eeeeeeeeeeeeeeeeeeeeeeeeee)eeee-8,8-eeeeeeee (888, M8=Me; M8=MM8Me); Meeeeee Meeeeeeee:[‌888‌]

MMMMMMM: Meeeeeeeeeee eeeeeee eee ee eeeeeeee ee eeeeeee ee eee eeeeeeeee eeeeeeeee.

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