Synthesis of the Mammea coumarins. Part 2. Experiments in the mammea E series and synthesis of mammea E/AC

摘要: From condensations between ethyl 4-acetoxy-3-oxohexanoate and acyl phloroglucinols, 5- or 7-acyl benzo[b]furans (5) were isolated rather than the desired 4-(1-acetoxypropyl)-5,7-dihydroxy-6(or 8)-acylcoumarins. Related 4-bromo-3-oxohexanoate, 4-chloro-3-oxobutanoate, phloroglucinols afforded either 4-(1-haloalkyl)-5,7-dihydroxy-6(or 8)-acylcoumarins, 6- 8-acylfuro[4,3,2,-d,e][1]benzopyran-4(2H)-ones (11) by subsequent dehydrohalogenation. Attempted conversion of 4-(1-haloalkyl)coumarins into 4-(1-acetoxyalkyl)coumarins with sodium acetate–acetic acid gave acylbenzofurans (5), silver acetate in acetonitrile acylfurobenzopyranones tetramethylammonium isomeric (13). Allyiic bromination 6-butyryl-5,7-dimethoxy-4-propylcoumarin 4-(1-bromopropyl) product to a 4-(1-acetoxypropyl)coumarin, followed difficult demethylation C-prenylation mammea E/AC, 6-acyl isomer one natural 8-acyl insecticidal Mammea coumarins; application this sequence 8-butyryl-5,7-dimethoxy-4-propylcoumarin failed at stage.