Acetoacetic isopropyl ester

After 8 hours boiling of solution of 3.8 g of 3 -nitro-benzylideneacetoacetic acid isopropylester, 8 grams of acetoacetic acid p-metoxyethyl ester and 6 ml cone ammonia in 80 ml ethanol under reflux, 2,6-dimethyl-4-(3 -nitrophenyl)-1,4-dihydropyridine 3-p-methoxyethyl ester 5-isopropyl ester of melting point 125°C (petroleum ether/ acetic ester) was obtained. Yield 49% of theory. 

Acetoacetic ester can be alkylated by isopropyl group if BF3 is saturated at low temperatures in the reaction mixture. 

Isopropyl anisole (171) was converted to bromide (172) by metalation, formylation and bromination. Alkylation with cyclopropyl ketoester produced (173) whose transformation to alcohol (174) was achieved by saponification, decarboxylation and reduction.. Its conversion to homoallylic bromide (175) was accomplished by the method of Julia et al. [56]. Alkylation of ethyl acetoacetate with bromide (175) furnished p-ketoester (176). It was subjected to cyclization with stannic chloride in dichloromethane. The resulting tricyclic alcohol provided the olefinic ester (177) by treatment with mesylchloride and triethylamine. Epoxidation followed by elimination led to the previously reported intermediate (146) whose conversion to triptolide (149) has already been described. 

In the presence of sodamide the anionic form of 2-amino-l-ethylbenzimidazole is substituted by alkyl halides on both the annular and exocyclic nitrogens. With butyl and isopropyl iodides the proportion of dialkylated product is increased. The synthetic utility of such nucleophilic reactions of 2-aminobenzimidazole is exemplified by reactions with ethyl cyanoacetate, acetoacetic ester and ethyl benzoylacetate, when subsequent cyclization of the initial products also gives pyrimidobenzimidazole derivatives (Scheme 117). 

Compounds containing active methylene groups can be alkylated by alcohols with loss of hydrogen from that position. For example, in the presence of boron trifluoride, isopropyl alcohol and ethyl acetoacetate give ethyl 2-iso-propylacetoacetate in 60-70% yield 643 the isopropyl group can be introduced in the same way into acetylacetone (2,4-pentanedione) 644 and reactions of xanthhydrol with malonic esters have also been recorded in the literature.645... 

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