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DOI: 10.1055/sos-SD-027-00847

Schobert, R.; Gordon, G. J.Science of Synthesis, (2004271045.

The viability of the above route to cumulated ylides 141 (X=NR1) (Scheme 50), although straightforward and high yielding, very much depends upon the purity of the starting materials, especially that of the dichloroimines 140 (X=NR1; Hal=Cl). Complete failures are reported in cases where substrates of dubious quality are used. A more robust four-step synthesis of cumulated ylides (Scheme 51) employs isothiocyanates, which when reacted with (methylene)triphenylphosphorane give ylides 142. In turn these products can be alkylated with bromo or iodomethane forming the phosphonium salts 143. Deprotonation of the latter with sodium methoxide leads to the stabilized ylides 144, the treatment of which with sodium hexamethyldisilazanide gives ylides 145 in overall yields as good as those reported for syntheses of analogous compounds described in Section[‌554‌]

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