Synthesis of Functionalized Diazoacetoacetates via Mukaiyama-type Condensations
Doyle, Michael P
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Mukaiyama-type condensation reactions of 3-<italic>tert</italic>-butyldimethylsiloxy-2-diazo-3-butenoate and different electrophiles are effective methods for the synthesis of highly substituted diazoacetoacetates. With 0.5-3 mol% of Zn(OTf)<sub>2</sub> as Lewis acid catalyst, Mukaiyama-Michael reactions of vinyldiazoacetates and &alpha,&beta-unsaturated ketones proceed at ambient temperature to afford functionalized diazoacetoacetates in good yields. By carefully choosing the reaction conditions, both Mukaiyama-Michael adducts in either silyl enol ether form or in ketone form can be synthesized. Addition products obtained from these Mukaiyama-Michael reactions are investigated in dirhodium(II) catalyst induced dinitrogen extrusion reactions. Enedione-diazoester derived from Mukaiyama-Michael reaction of 3-<italic>tert</italic>-butyldimethylsiloxy-2-diazo-3-butenoate and 4-methoxy-3-bute-2-one can be converted to resorcinol derivatives under base catalysis. This novel transformation was investigated and developed into a synthetic methodology for the preparation of poly-substituted resorcinol compounds. Orthoesters also react with 3-<italic>tert</italic>-butyldimethylsiloxy-2-diazo-3-butenoate in the presence of Lewis acid catalysts. Diazoacetoacetates that contain acetal functionality can be assembled by these reactions. Rhodium(II) acetate promoted dinitrogen extrusion reactions of these adducts can give &beta-alkoxycyclbutanone products, which are useful synthons in organic synthesis.