Aldehydes Perkin condensation

Condensation between anhydrides and aldehydes (Perkin) Condensation between P-carboxy phosphoranes and aldehydes or ketones... 

Perkin condensation is the reaction between aromatic aldehydes and aliphatic acid anhydrides (in the presence of the sodium salt) to form p-arylacrylic acid... 

The anhydride also undergoes a Perkin condensation with aromatic aldehydes in the presence of a base to give l-oxo-3-phenylisochroman-4-carboxylic acids (58JCS2612). 

The mechanism of the Perkin condensation involving benzal acetate has been revised.17 It has been demonstrated that the enolate of the gem-diacetate derived from the aromatic aldehyde and acetic anhydride-rather than the enolate of acetic anhydride itself-adds to the aldehyde in the key step. The deprotonation of the diacetate to the enolate appeared to be assisted electrophilically by the neighbouring acetate group. 

The base-catalyzed reaction of an aldehyde (having no a hydrogens) with an anhydride is called the Perkin condensation. Propose a mechanism for the following example of the Perkin condensation. (Sodium acetate serves as the base.)... 

Paraconic acids, pyrolysis, 54 Perkin condensation, 52 Phenolic aldehydes, preparation, 281, 282... 

Perkin-Fittig Synthesis.—The first step in the synthesis is analogous to the aldol condensation. It consists in the addition of a sodium salt of an acid, usually acetic acid, to a saturated aldehyde, whereby condensation is effected and a > /a-hydroxy acid is formed. The beta-... 

There are several general ways to make compounds of this kind the aidol condensation, to make unsaturated aldehydes and ketones dehydrohalogenation of a-halo acids and the Perkin condensation, to make unsaturated acids. Besides these, there are certain methods useful only for making single compounds. 

The simplest synthesis of coumarins is a special case of the Perkin condensation, i.e. the condensation of an aromatic aldehyde with an anhydride. orthoAdyAmxy-trans-cmnaimc acids cannot be intermediates since they do not isomerise under the conditions of the reaction nor can 0-acetylsalicylaldehyde be the immediate precursor of the coumarin, since it is not cyclised by sodium acetate on its own. ... 

Simple aliphatic or aromatic ketones are not suitable substrates in the Pericin transformation. Similarly, aliphatic aldehydes are not generally acceptable components in this reaction. This long-known limitation was studied by Crawford and Little. They demonstrated that many aliphatic aldehydes give diacetates and enol acetates when heated with acetic anhydride, with or without sodium acetate, suggesting this side reaction causes the typical Perkin process to fail. Semmeler had previously obtained similar results. They did show, however, that several short chain aldehydes, as well as frowj-citral (16), undergo the Perkin condensation with p-nitrophenylacetic anhydride the p-nitrophenyl substituent activates the anhy-... 

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-... 

Phthalic anhydride, when used as the carbonyl component in the Perkin reaction, affords, on treatment with acetic anhydride and potassium acetate, phthalylacetic acid (15 equation 12).24 a-Arylacetic acids also react with aromatic aldehydes to afford a-arylcinnamic acids (Ogliaro modification of the Perkin condensation, equation 7) 1 this type of reaction presumably involves die formation of the mixed anhydride of phenylacetic acid and acetic acid and/or phenylacetic anhydride. This modification is also illustrative of the equilibrium that is established between acid, acid salt and acid anhydrides under the conditions of the reaction. 

The Perkin condensation is an aldol-type condensation in which an aromatic aldehyde (ArCHO) reacts with a carboxyUc acid anhydride, (RCH2C0)20, to give an a,j8-unsaturated acid (ArCH = CRCO2H). The catalyst that is usually employed is the potassium salt of the carboxylic acid (RCH2CO2K). (a) Outline the Perkin condensation that takes place when benzaldehyde reacts with propanoic anhydride in the presence of potassium propanoate. (b) How would you use a Perkin condensation to prepare />-chlorocinnamic acid, />-CIC6H4CH = CHC02H ... 

Perkin condensation Aldehyde H Anhydride 0 CH3 " 0 CH3 0 Sodium acetate (CH3C02Na) H OH... 

Perkin condensation a condensation of an aromatic aldehyde and acetic acid, pericyclic reaction a concerted reaction that takes place as the result of a cyclic rearrangement of electrons. 

The Erlenmeyer azlaetone synthesis consists in the condensation of an aldehyde with an acylglycine in the presence of acetic anhydride (and usually sodium acetate). It is a special case of the Perkin condensation and assueh has been discussed briefly by Johnson. ... 

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