Ruzicka cyclisation

Ruzicka cyclisation The reaction of a long chained dicarboxylic acid with Th02 to form a cyclic... 

The first syntheses [172] of macrocyclic scented compound were based on the Piria cyclisation (Raffaele Michele Rocco Piria (1814-1865), Italian chemist) of terminally functionalised aliphatic precursors. Thus, pyrolysis of the thorium salt of thapsic acid (Fig. 3.42) and purification via the semicarbazone gave exaltone in a yield of 5.5 % (Ruzicka cyclisation). The mechanism ofthis reactionhas not been finally established, although it is accepted that free radicals are involved in the cyclisation. [173] Oxidation using Caro s acid then gives exaltolide in 47 % yield. 

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