Tungsten chloride-Butyllithium

Kupchan et al. achieved the first total synthesis of aristolochic acid involving photocyclization of substituted 2-iodostilbenes [410], Piperonal (689) provided a suitable skeleton to build ring A of aristolochic acid. It was reduced to the piperonoyl alcohol (690) with lithium aluminium hydride. Bromination of 690 afforded 6-bromopiperonoyl bromide (691). It was then hydrogenated to the corresponding 2-bromo-4,5-methylenedioxytoluene by w-butyllithium carbonation method. The toluic acid (693) was converted to acid chloride by oxalyl chloride, and bromination of acid chloride and by radiation with a 200-W tungsten lamp followed by methanolysis afforded the ester 694, which on treatment with silver nitrate produced methyl ester (695). 

DEOXYGENATION, EPOXIDES Ferric chloride-n-Butyllithium. Potassium seleno-cyanate. Sodium cyclopentadienyldicarbonylferrate. Tungsten hexachloride. 

Related Reagents. t-Butoxide Methyllithium Tungsten(VI) Chloride-n-Butyllithium n-ButyUithium-Lithium Dimethyl-aminoethanol s-Butyllithium and r-Butyllithium. 

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