Claisen-Schmidt reaction intramolecular

Nucleophilic addition to C=0 (contd.) ammonia derivs., 219 base catalysis, 204, 207, 212, 216, 226 benzoin condensation, 231 bisulphite anion, 207, 213 Cannizzaro reaction, 216 carbanions, 221-234 Claisen ester condensation, 229 Claisen-Schmidt reaction, 226 conjugate, 200, 213 cyanide ion, 212 Dieckmann reaction, 230 electronic effects in, 205, 208, 226 electrons, 217 Grignard reagents, 221, 235 halide ion, 214 hydration, 207 hydride ion, 214 hydrogen bonding in, 204, 209 in carboxylic derivs., 236-244 intermediates in, 50, 219 intramolecular, 217, 232 irreversible, 215, 222 Knoevenagel reaction, 228 Lewis acids in, 204, 222 Meerwein-Ponndorf reaction, 215 MejSiCN, 213 nitroalkanes, 226 Perkin reaction, 227 pH and, 204, 208, 219 protection, 211... 

The intramolecular carbon-carbon bond-forming reactions considered in this section are based on the aldol condensation (see Section 5.18.2, p. 799), the Claisen-Schmidt reaction (see Section 6.12.2, p. 1032), the Claisen ester condensation (see Section 5.14.3, p. 736), and the Claisen reaction (see Section 6.12.2, p. 1032). Since these carbonyl addition reactions are reversible, the methods of synthesis are most successful for the formation of the thermodynamically stable five- and six-membered ring systems. The preparation of the starting materials for some of these cyclisation reactions further illustrates the utility of the Michael reaction (see Section, 5.11.6, p. 681). 

Wrobel and Golfbiewski (67) interpreted the condensation in terms of a two stage reaction a Claisen-Schmidt condensation resulting in an amino alcohol (147) followed by nucleophilic intramolecular substitution of the OH group. Quick and Oterson (69) suggested a modification of the latter... 

Flavanones 25 are often synthesized by Claisen-Schmidt condensation followed by intramolecular Michael addition reaction of the corresponding chalcone derivative. Climent et al. reported a new environment-friendly method to prepare flavanones 25 by the reaction of 5-substituted-2-hydroxyacetophenones and benzaldehydes using hydro-talcites as basic catalysts (Scheme 16) [81]. Substitution over both aromatic rings influenced the reaction coxu-se leading to flavanones 25 in 7-45% of yields in only Ih of reaction time. 

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