Dealkylation silyl ether

Lead tetraacetate was employed by Stoodley and coworkers for an oxidative isomerization in their synthesis of 4-demethoxydaunomycinone (47). The diene (48) reacted with the oxirane dienophile (49) via the least hindered endo transition state to give the cycloadduct (50) in 86% yield. Hydrolysis of the silyl enol ether followed by reduction of the oxirane and introduction of the acetylene moiety gave the compound (51), which was oxidatively isomerized with LTA in acetic acid to give the quinone (52). All that remained now to complete the synthesis was conversion of the acetylene to a methyl ketone and dealkylation of the ether, llie last two steps were accomplished in an over l yield of 38%, the low yield attributable to problems in formation of the hydroxy group from the ether (Scheme 11). Bulman-Page and Ley employed LTA for a similar transformation in their synthesis of demethoxydaunomycinone and related anthracyclinones. 

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