Salicylaldehyde purification

Synthesis of complex 1. The pentadentate salen catalyst 1 was synthesized as described (9). In short, the tosylated 2-[2-(2-methoxyethoxy)-ethoxy]-ethanol 2 (10) was reacted with 2,4-dihydroxybenzaldehyde 3 to yield 4-alkoxy salicylaldehyde 4 after chromatographic purification (eq. 1). Subsequent condensation of 4 with 1,3-diaminopropanol yielded water-soluble salen ligand 5 in sufficient purity and 89% yield (11). The formation of an azomethine bond is indicated by a shift of the NMR signal for the carbonyl carbon from 194.4 ppm in aldehyde 4 to 166.4 ppm for the imino carbon in 5. The pentadentate ligand 5 was then treated with copper(ll) acetate in methanol to obtain the dinuclear copper(ll) complex 1 as a green solid (eq. 2) (11). 

Removal of unchanged salicylaldehyde by steam distillation (followed conveniently by testing the distillate with 2,4-dinitro-phenylhydrazine reagent) provides a product sufficiently pure for use in the next step. Also, the recovered salicylaldehyde can be used again without further purification. 

Bis(salicylaldehyde)diimine complexes of cobalt take up and release molecular oxygen with such efficiency that they have been made use of for the purification of oxygen.66... 

The original literature records the preparation of many hundreds of spiropyrans and is the place to look first for a specific compound. Some generalities about the best choice of intermediates and reaction conditions have been given in Section 1.2. Presented here, with an emphasis upon manipulative details, are descriptions of preparations of a typical BIPS on a large laboratory scale (in which the condensation intermediates can be observed) a Fischer s base via a Plancher rearrangement, where the reaction and purification are complex and a salicylaldehyde having a group useful for various further transformations. 

Place 4,4-methylenedianiline (1.6 g, 8 mmol) and ethanol (25 mL) in a 100 mL conical flask equipped with a stirrer bar. Stir at room temperature for about 20 min or until all the solid has dissolved. Add a solution of salicylaldehyde (1.9 g, 1.7 mL, 15 mmol) in ethanol (25 mL) and continue to stir. The solution turns an intense yellow colour before the product precipitates over 30 min as a yellow powder. The product is isolated in quantitative yield by filtration and washed with small quantities of ethanol to remove any unreacted starting materials. N,N -(4,4 -methylenebiphenyl)bis(salicylideneimine) (6) is isolated as a yellow microcrystal-line powder. Further purification should not be necessary, however, the product can be recrystallized from a minimum volume of boiling ethanol. 

Salicylaldehyde, 28, 24 purification of, 28, 25 Salicylanilides, from various amines, 26, 93... 

The required tetraaldehyde 156 was prepared by alkylation of salicylaldehyde (157) with bromoethanol to yield 158, followed by condensation with pyromellitoyl chloride 159. Reaction of the tetraaldehyde with pyrrole in refluxing propionic add yielded the capped porphyrin 160 after chromatographic purification ( heme 46) (Fig. 5) ... 

Af -Disalicylalethylenediamine. The salicylaldehyde is purified by the process of shaking or by standing in contact with powdered calcium carbonate, followed by distillation. To a solution of 244 g. (2 mols) of the purified material in 1 1. of boiling 95 per cent ethyl alcohol is added 60.1 g. (1 mol) of ethylenediamine this is measured by weighing out the appropriate amount of aqueous solution. If the concentration of the ethylenediamine is not known within a few per cent, a sample should be titrated against a standard acid, using methyl red as indicator. In 20 to 30 seconds the mass becomes sohd with formation of a bri t yellow, crystalline material. The reaction mixture is cooled and filtered on a Buchner fimnel, and the precipitate is spread in thin layers on absorbent paper to dry. It may be recrystallized from 61. of hot 95 per cent alcohol or used without further purification. It will dissolve somewhat more readily in the next step if it is not allowed to dry completely. Yield, 255 g. (95 per cent). The compound melts at 123°. 

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