Silyl syntheses

Withasomnine Pyrazole, 1-phosphoryl-reactions, 5, 271 Pyrazole, 1-silyl-synthesis, 5, 236 Pyrazole, 1-stannyl-synthesis, 5, 236 Pyrazole, 1-styryl-synthesis, 5, 233 Pyrazole, 1-thienyl-reactions, 5, 268 Pyrazole, 4-(2 -thienyl)-nitration, 5, 238 Pyrazole, 4-(3 -thienyl)-nitration, 5, 238 Pyrazole, trifluoromethyl-synthesis, 5, 284... 

The (partial) description of the synthesis and coupling of the five fragments starts with the cyclohexyl moiety C —C. The first step involved the enantio- and diastereoselective harpless epoxidation of l,4-pentadien-3-ol described on p. 126f. The epoxide was converted in four steps to a d-vinyl d-lactone which gave a 3-cyclohexenecarboxylate via Ireland-CIaisen rearrangement (cf. p. 87). Uncatalysed hydroboration and oxidation (cf. p. 131) yielded the desired trans-2-methoxycyclohexanol which was protected as a silyl ether. The methyl car-... 

In the prostaglandin synthesis shown, silyl enol ether 216, after transmetaJ-lation with Pd(II), undergoes tandem intramolecular and intermolecular alkene insertions to yield 217[205], It should be noted that a different mechanism (palladation of the alkene, rather than palladium enolate formation) has been proposed for this reaction, because the corresponding alkyl enol ethers, instead of the silyl ethers, undergo a similar cyclization[20I],... 

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