Mediated coupling conjugated ketones

Retrosynthetically, a base-catalyzed dimerization of 127 would afford stephacidin B. Avrainvillamide (127) was simplified as vinyl iodide 128 by cleavage of the dihydropyrano [2,3-g]indole-l-oxide moiety and palladium mediated coupling. An aminoacyl radical addition from 129 gave access to 128, while 129 could be derived from cyanide 130 through a hemiaminal formation/dehydration and conjugate addition. Finally, Strecker-like reaction of ketone 131 would fulfill nitrile 130 [55] (Scheme 22). 

The 3.8-nonadienoate 91, obtained by dimerization-carbonylation, has been converted into several natural products. The synthesis of brevicomin is described in Chapter 3, Section 2.3. Another royal jelly acid [2-decenedioic acid (149)] was prepared by cobalt carbonyl-catalyzed carbonylation of the terminal double bond, followed by isomerization of the double bond to the conjugated position to afford 149[122], Hexadecane-2,15-dione (150) can be prepared by Pd-catalyzed oxidation of the terminal double bond, hydrogenation of the internal double bond, and coupling by Kolbe electrolysis. Aldol condensation mediated by an organoaluminum reagent gave the unsaturated cyclic ketone 151 in 65% yield. Finally, the reduction of 151 afforded muscone (152)[123]. n-Octanol is produced commercially as described beforc[32]. 

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