Perkin condensation intramolecular

Similar in style to the above are the base-catalyzed intramolecular cyclizations of diesters (116) and substituted salicylaldehydes (117), Dieckmann and Perkin condensations, respectively (36JCS212, 36JCS419, 40JCS787). 

An important variation of the Perkin reaction is the Erlenmeyer azalactone synthesis exemplified by equation (4), involving condensation of an aldehyde and an N-acylglycine derivative in the presence of acetic anhydride and sodium acetate. Although this reaction, analogous to the classical Perkin condensation, was initially limited to the use of aromatic aldehydes, Baltazzi and Robinson reported that the use of lead acetate and THF allowed the preparation of several azalactones derived from aliphatic aldehydes (equation 15). The results for the condensation of several aldehydes and ketones with hippuric acid (28) under these conditions are shown in Table 2. The reaction proceeds through the intermediate (26) (intramolecular condensation of 25), which reacts with the aldehyde in Perkin fashion to provide the so-called azalactone product (Scheme 8). It is the formation of such oxazolones from acylamino acids which is be-... 

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... 

Intramolecular aldol/Perkin type condensation of orf/to-formylaryloxyacetic acids and arylthioacetic esters produces benzofuran- and benzothiophene-2-esters respectively, as illustrated below. The synthesis can be performed in one pot, thus ortfto-hydroxyaryl-aldehydes or -ketones, are 0-alkylated with a-halo-ketones, then intramolecular aldol condensation in situ produces 2-acyl or 2-aroyl-benzofurans. ° For benzothiophenes, the ring-closure substrates can also be obtained via methyl thioacetate displacement of fluoride from orf/to-fluoro-araldehydes. ... 

The generally accepted mechanism for the Perkin reaction is shown in Scheme 2. Much of the early woik leading to this view, which was the result of numerous investigations spanning a period of greater than SO years, has been reviewed in some detail. Formation of the anhydride enolate (1) and aldol-type condensation generates the alkoxide anhydride (2). Intramolecular acylation provides an acetoxycaibox-ylate (3), which forms a mixed anhydride elimination of acetic acid and hydrolysis affords the unsatu-... 

Laks, RE., R.W. Hemingway, and A.H. Conner Condensed Tannins. Base-catalyzed Reactions of Polymeric Procyandins with Phloroglucinol Intramolecular Rearrangements. J. Chem. Soc., Perkin Trans. 1, 1875 (1987). 

Intramolecular aldol/Perkin type condensation of aryloxyacetic acids and arylthioacetic esters produces benzofuran and benzothiophene-2-esters respectively. The examples shown illustrate contrasting methods - classical and modem - for the preparation of the required starting materials. 

Laks P E, Hemingway R W, Conner A H (in press) Condensed tannins Base-catalysed reactions of polymeric procyanidins with phloroglucinol. Intramolecular rearrangements. J Chem Soc Perkin Trans I... 

Viviers P M, Kolodziej H, Young D A, Ferreira D, Roux D G 1983 Synthesis of condensed tannins. Part II. Intramolecular enantiomerism of constituent units of tannins from the Anacar-diaceae Stoichiometric control in direct synthesis, derivation of IH nuclear magnetic resonance parameters applicable to higher oligomers. J Chem Soc Perkin Trans I 2555-2562... 

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