Acetoacetate dianion

Where will alkylation tend to occur on the ethyl acetoacetate dianion 73 Answer... 

Claisen condensation of acetoacetate dianion.3 In the presence of BF3 etherate the dianion of acetoacetate undergoes Claisen condensation with the tetra-methyldiamides of dicarboxylic acids 1 to form polyketides (2, equation I). The... 

In Chapter 24, we introduced the idea that the last-formed anion in a dianion or trianion is the most reactive. Methyl acetoacetate is usually alKylated on the central carbon atom because that is the site of the most stable enolate. But methyl acetoacetate dianion—formed by removing a second proton from the... 

The l,3-bis(trimethylsililoxy)butadienes 130-132, as the equivalent of methyl acetoacetate dianion, constitute the three-carbon fragments with two nucleophilic sites (equation 110). Condensation of 130-132 with various equivalents of -dicarbonyl compounds and titanium(IV) chloride gives substituted methyl salicylates. The differential reactivity of the electrophiles which increases in the order conjugated position of enone > ketone > monothioacetal, acetal and of 130-132 (4-position > 2-position) ensures complete regioselectivity in this combination of two three-carbon units to form phenols such as 133 and 134 °° °. ... 

Yamaguchi has reported a related biomimetic synthesis of anthraquinones, summarized in Scheme Reaction of diester (165) with methyl acetoacetate dianion provides a tetraketo diester which is cy-clized by calcium hydroxide to obtain anthrone (166). Air oxidation in basic medium affords the anthra-quinone (167). 

In the presence of LiC104 the alkylation of the ethyl acetoacetate dianion with epibro-mohydrin leads to 2-ethoxycarbonylmethylene-5-hydroxymethyltetrahydrofuran. ... 

The dianion of acetoacetate undergoes Claisen condensations with tetramethyldiamide derivatives of dicarboxyhc acids to produce polyketides in the presence of BF3-OEt2 (eq 15). Similarly, 3,5-dioxoalkanoates are synthesized from tertiary amides or esters with the acetoacetate dianion in the presence of Bp3-OEt2 (eq 16). ... 

Scheme XXXL Synthesis of the 2,7-epimeric analog of perhydrohistrionicotoxin and a 2,7-epi-dioxa analog (75). A i) Methyl acetoacetate dianion, hexamethylphosphoric triamide, ii) Pyrrolidine. B i) 0s04, ii) NaHSOa, iii) Ag2C03, iv) Triethylphosphonoacetate anion. C i)NH3. D i) Toluenesulphonic acid, ii)NaBH4, iii) Phosgene. E i) Al(i-Bu)2H, ii)Allyl-dimethylphenylphosphonium bromide, potassium methylsulfinylmethylide. F i) Pd/C, H2, ii) Li, CH3NH2. G i) LiBH4, ii) KH, C2H5I, iii) Li, CH3NH2...

---