Chapter_19 - P1: QZI/SRB JWDD052-19 P2: xxx...

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P1: QZI/SRB P2: xxx Printer: Hamilton JWDD052-19 JWDD052-Solomons-v3 May 2, 2007 12:56 19 SYNTHESIS AND REACTIONS OF β -DICARBONYL COMPOUNDS: MORE CHEMISTRY OF ENOLATES SUMMARY OF ACETOACETIC ESTER AND MALONIC ESTER SYNTHESES A. Acetoacetic Ester Synthesis O O OEt O O OEt (1) NaOEt (2) RX (1) tert -BuOK (2) R ' X RH O O OEt (1) OH , H 2 O (2) H 3 O + RR ' O O OH heat CO 2 ' O R R ' B. Malonic Ester Synthesis O O OEt EtO O O OEt EtO (1) NaOEt (2) RX (1) tert -BuOK (2) R ' X O O OEt EtO ' (1) OH , H 2 O (2) H 3 O + O O OH HO HO heat CO 2 ' O R R ' SOLUTIONS TO PROBLEMS 19.1 (a) O OEt H O OEt + Ο Et + EtOH O OEt Step 1 396
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P1: QZI/SRB P2: xxx Printer: Hamilton JWDD052-19 JWDD052-Solomons-v3 May 2, 2007 12:56 SYNTHESIS AND REACTIONS OF β -DICARBONYL COMPOUNDS 397 O Step 2 OEt O OEt + + O O OEt EtO O O OEt EtO O O OEt H O O OEt + OEt + EtOH Step 3 (b) O O OEt OH O OEt + 19.2 (a) O O OEt (b) To undergo a Dieckmann condensation, diethyl 1,5-pentanedioate would have to form a highly strained four-membered ring. 19.3 O OEt + EtO + EtOH O OEt O OEt + O OEt C 6 H 5 O OEt OEt C 6 H 5 O O O OEt C 6 H 5 + EtO + EtOH O O OEt C 6 H 5 C 6 H 5 O O OEt H 3 O + O OEt + EtO + EtOH C 6 H 5 O OEt C 6 H 5
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P1: QZI/SRB P2: xxx Printer: Hamilton JWDD052-19 JWDD052-Solomons-v3 May 2, 2007 12:56 398 SYNTHESIS AND REACTIONS OF β -DICARBONYL COMPOUNDS + + EtO + EtOH O OEt EtO O O OEt EtO C 6 H 5 H 3 O + O OEt C 6 H 5 O OEt EtO EtO C 6 H 5 O O O OEt EtO C 6 H 5 O O OEt EtO C 6 H 5 Resonance stabilized 19.4 O (a) (b) OEt + O OEt + O O OEt H O EtO OEt (1) NaOEt (2) H 3 O + (1) NaOEt (2) H 3 O + O O O OEt OEt O OEt H O 19.5 O O + + (1) NaOEt (2) H 3 O + (1) NaOEt (2) H 3 O + (1) NaOEt (2) H 3 O + O OEt H O H (a) (b) (c) (1) NaOEt (2) H 3 O + O O O O OEt O O OEt EtO O O EtO OEt O O EtO O OEt OEt O OEt O O O OEt
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P1: QZI/SRB P2: xxx Printer: Hamilton JWDD052-19 JWDD052-Solomons-v3 May 2, 2007 12:56 SYNTHESIS AND REACTIONS OF β -DICARBONYL COMPOUNDS 399 19.6 O EtO O O O O O Η + EtO + EtOH + EtO O O H 3 O + O OEt O O O EtO EtOH 19.7 The partially negative oxygen atom of sodioacetoacetic ester acts as the nucleophile. O O O O - OEt OEt - 19.8 Again, working backward, O O O O OH O O OEt O O OH O O OEt heat CO 2 heat CO 2 (1) NaOEt (2) EtBr (1) dil. NaOH, heat (2) H 3 O + (1) dil. NaOH, heat (2) H 3 O + (a) (b) O O O O OEt (1) tert -BuOK (2) Br (1) NaOEt (2) Br OEt O O OEt
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P1: QZI/SRB P2: xxx Printer: Hamilton JWDD052-19 JWDD052-Solomons-v3 May 2, 2007 12:56 400 SYNTHESIS AND REACTIONS OF β -DICARBONYL COMPOUNDS O C 6 H 5 heat CO 2 O O OH (1) OH, heat (2) H 3 O + C 6 H 5 (1) NaOEt (2) Br O O OEt O O OEt C 6 H 5 C 6 H 5 (c) 19.9 (a) Reactivity is the same as with any S N 2 reaction. With primary halides substitution is highly favored, with secondary halides elimination competes with substitution, and with tertiary halides elimination is the exclusive course of reaction. (b) Acetoacetic ester and 2-methylpropene (isobutylene) (c) Bromobenzene is unreactive to nucleophilic substitution.
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Chapter_19 - P1: QZI/SRB JWDD052-19 P2: xxx...

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