Wittig homologation

Wilkinson s catalyst 117,345,777 Wittig condensation 73 Wittig homologation 503 Wittig methylenation 649 Wittig reaction 17, 68 f., 86 f.,... 

Stork s strategy towards racemic morphine comprises a Diels-Alder cycloaddition reaction of a benzofuran to establish the B- and C-ring of morphine as the key step [53]. The reaction sequence started with the ketahzation of iodoisovaniUin 97 (Scheme 15). Subsequently, the phenol was reacted with methyl propiolate to afford 98 as precursor for the installation of the benzofuran moiety via a palladium-catalyzed Heck cyclization (99). Next, the key intermediate was prepared for the Diels-Alder reaction. Hydrolysis of the acetal under acidic conditions and Wittig homologation afforded aldehyde 100, which was converted to diene 101 via hydrozirconation of acetylene 105 employing the Schwartz reagent and subsequent reaction with aldehyde 100 followed by sUylation of the secondary alcohol. 

A synthesis of castanospermine has been described commencing with the chiral lactam 268. A -Allylation, selective primary benzyl-acetyl exchange, deacylation, oxidation and Wittig homologation gave 269. Metathesis reaction gave the... 

Sphingosine 319 has also been prepared from D-xylose derivative 320, and also then converted to ceramide 324. Wittig homologation and mesylation of320 gave 321, which underwent Sn2 substitution to give intermediate 322, elaborated by standard means to 323 and thence 324 (Scheme 28). ... 

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