578 ESTER EN。 LATES H3C- H. +“ OCH.CH CH3CH 21.5 The desired ketone, cyclopentanone, is derived from the corresponding B-keto ester. This key intermediate is obtained from a Dieckmann cyclization of the starting material, diethyl hexanedioate. COCH. CH CHaCH,O, C(CH,), CH First treat the diester with sodium ethoxide to effect the Dieckmann cyclization L. NaOCHCI COCHCH CH, CH,OCCH, CH, CH, CH,COCH Ch3 2Hao Diethyl hexanedioate Ethyl (2-oxo Next convert the B-keto ester to the desired product by saponification and decarboxylation. COCHCH 3. heat Ethyl (2-oxocyclopentane)- 21.6(b) Write a structural formula for the desired product; then disconnect a bond to the a-carbon CH,3CH,CCH CH CHCCH Derived from alkyl halide Therefore 1. NaOCH, CH -CH Br+CH, CCH,COCH- CH, 2.HO",H,0 CH,CH,CCH3 4. heat Benzyl bromide Ethyl acetoacetate pheny l-2-butano Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website578 ESTER ENOLATES 21.5 The desired ketone, cyclopentanone, is derived from the corresponding -keto ester. This key intermediate is obtained from a Dieckmann cyclization of the starting material, diethyl hexanedioate. First treat the diester with sodium ethoxide to effect the Dieckmann cyclization. Next convert the -keto ester to the desired product by saponification and decarboxylation. 21.6 (b) Write a structural formula for the desired product; then disconnect a bond to the -carbon atom. Therefore CH2CH2CCH3 O Benzyl bromide 4-Phenyl-2-butanone CH2Br Ethyl acetoacetate CH3CCH2COCH2CH3 O O 1. NaOCH2CH3 2. HO, H2O 3. H 4. heat CH2 CH2CCH3 O Required alkyl halide CH2 X Derived from ethyl acetoacetate CH2CCH3 O COCH2CH3 O O Ethyl (2-oxocyclopentane)- carboxylate O Cyclopentanone 1. HO, H2O 2. H 3. heat CH3CH2OCCH2CH2CH2CH2COCH2CH3 O O 1. NaOCH2CH3 2. H3O COCH2CH3 O O Ethyl (2-oxocyclopentane)- carboxylate Diethyl hexanedioate CH3CH2O2C(CH2)4CO2CH2CH3 O COCH2CH3 O O O O H3C OCH2CH3 O O H3C CH3CH2O 2-Methyl-1,3- cyclopentanedione Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website