1559T.ch25.439-45310/20/055:59 AM Page4a6 EQA 446.chapter 25 HETEROCYCLES:HETEROATOMS IN CYCLC ORGANIC COMPOUNDS (e)Paal-Knorr 0 0 HCCH-CHCH NH product CHs CHs 0 CH.CCHs 37 0 CH,CHO O O OCH CH 0 ⊕ CH Compare synthesis of furans,etc.,from 1.4-diketones 38.Protonation of keto C00褥o9(c) Paal-Knorr (d) 37. Compare synthesis of furans, etc., from 1,4-diketones. 38. Protonation of ketones and aldehydes can give rise to electrophiles capable of aromatic substitution: Then, H OH  N H N H H H HO N H H HO H H O H OH  H OH  CH2 CH3CH2OC O O COCH2CH3 O O O C C C CH2 HCl, H2O (With ester hydrolysis) HOOC O O COOH CH3CCH3 O CH3CH2O CH3CH2O OCH2CH3 OCH2CH3 O O O C  O C C C NaOCH2CH3, CH3CH2OH Double Claisen condensation O O H CH3 CH3 CH3 CH3 S P2S5, O O product CH3 CH3 HCCH CHCH NH3 446 • Chapter 25 HETEROCYCLES: HETEROATOMS IN CYCLIC ORGANIC COMPOUNDS 1559T_ch25_439-453 10/20/05 5:59 AM Page 446