Salicyl-aldehyde

Benzaldehyde, benzoin, cinnamic aldehyde, salicylic aldehyde, furfurol, and quinone, under the influence of the discharge, absorb nitrogen more or less rapidly. 

Action of sodium hydroxide. Does not undergo the Cannizzaro reaction. It dissolves in dil. NaOH solution, giving a yellow solution from which the aldehyde is precipitated unchanged on acidification. If heated with cone. NaOH solution, salicylaldehyde slowly undergoes atmospheric oxidation to salicylic acid. 

In the strongly basic medium, the reactant is the phenoxide ion high nucleophilic activity at the ortho and para positions is provided through the electromeric shifts indicated. The above scheme indicates theorpara substitution is similar. The intermediate o-hydroxybenzal chloride anion (I) may react either with a hydroxide ion or with water to give the anion of salicyl-aldehyde (II), or with phenoxide ion or with phenol to give the anion of the diphenylacetal of salicylaldehyde (III). Both these anions are stable in basic solution. Upon acidification (III) is hydrolysed to salicylaldehyde and phenol this probably accounts for the recovery of much unreacted phenol from the reaction. 

Fig. 8.6. pH-Rate profile for release of salicylic acid fiom benz-aldehyde disalicyl acetal. [Reproduced firom E. Anderson and T. H. Fife, J. Am. Chem. Soc. 95 6437 (1973) by permission of the American Chemical Society.]... 

Phenolic resins were the first totally synthetic plastics invented. They were commercialized by 1910 [I]. Their history begins before the development of the structural theory of chemistry and even before Kekule had his famous dreams of snakes biting their tails. It commences with Gerhardt s 1853 observations of insoluble resin formation while dehydrating sodium salicylate [2]. These were followed by similar reports on the behavior of salicylic acid derivatives under a variety of reaction conditions by Schroder et al. (1869), Baeyer (1872), Velden (1877), Doebner (1896 and 1898), Speyer (1897) and Baekeland (1909-1912) [3-17]. Many of these early reports appear to involve the formation of phenolic polyesters rather than the phenol-aldehyde resins that we think of today. For... 

The reaction of methoxybutenone with salicylic aldehyde (20°C, MeOK, toluene, MeOH, 15 h) affords 3-acetyl-2-methoxy-chromo-3-ene (291) in 14% yield (80MI1). 

The Dakin reaction proceeds by a mechanism analogous to that of the Baeyer-Villiger reaction. An aromatic aldehyde or ketone that is activated by a hydroxy group in the ortho or para position, e.g. salicylic aldehyde 12 (2-hydroxybenzaldehyde), reacts with hydroperoxides or alkaline hydrogen peroxide. Upon hydrolysis of the rearrangement product 13 a dihydroxybenzene, e.g. catechol 14, is obtained ... 

The formylation of a phenol 1 with chloroform in alkaline solution is called the Reimer-Tiemann reaction. It leads preferentially to formation of an ortho-formylated phenol—e.g. salicylic aldehyde 2 —while with other formylation reactions, e.g. the Gattermann reaction, the corresponding /jara-formyl derivative is obtained as a major product. The Reimer-Tiemann reaction is mainly used for the synthesis of o-hydroxy aromatic aldehydes. 

It is soinble in about 1 volumes of IQ 24 volumes of "0 per cent, alcohol. I /H-piuene and tracea ot salicylic aud honicol was cousidered probable, but Phellaudrecc was not present, and u aldehydes or ketones, phenols or camphor. The chief conatitnent pinene, a mixture of the dextro-aud laevo-rotatory vatielief... 

Salicylic aldehyde, C HgOj, is the simplest representative of the ortho-hydroxy aldehydes, which are, generally speaking, strongly odorous... 

Salicylic aldehyde is an almost colourless oil with a fragrant odour of meadowsweet. Its constitution is as follows —... 

Coumarin was first produced synthetically by Perkin. He made it by heating salicylic aldehyde, CgH (OH)i(COH), acetic anhydride, and sodium acetate. The whole solidifies to a crystalline mass, from which, on treatment with water, an oil separates containing coumarin and aceto-coumaric acid. This acid on heating is decomposed into acetic acid and coumarin, so that the product of distillation is principally coumarin. Perkin s synthesis proceeds according to the following equation —... 

Coumarin is sometimes adulterated with acetanilide, which should always be looked for the ease with which it yields aniline, on heating with potash solution, renders it very easy of detection. Some samples, otherwise pure, contain traces of unaltered salicylic aldehyde, which is revealed by the odour. 

Sodium Salicylate.—When an aldehyde is shaken with a saturated solution of sodium salicylate, there seems to be evidence of the formation of a weak molecular compound, and with cinnamic aldehyde well-defined crystals have been obtained which give on analysis —... 

S g of ethyl glycinate hydrochloride were dissolved in 400 cc of ethanol and 33.5 g of salicylic aldehyde were added. It is refluxed for half an hour and cooled. 38 cc of triethylamlne and 25 g of Raney nickel are then added whereafter hydrogenation is carried out at room temperature and under atmospheric pressure. After hydrogen adsorption was complete, the mixture was filtered and the alcohol evaporated off. The residue was taken up with acidified water, extracted with ether to eliminate part of the by-products, consisting mainly of o-cresol, then made alkaline with ammonia and extracted with ethyl acetate. The solvent was removed in vacuo and the residue crystallized from ether/petroleum ether. 36.7 g of o-hydroxybenzyl-aminoacetlc acid ethyl ester melting at 47°C are obtained. 

Chloroacetic acid, reaction with salicyl-aldehyde, 46, 28 Chloroacetone, 46, 3 Chloroacetyl fluoride, 45, 6 o-Chloroacetyl isocyanate, 46,16 -Chloroaniline, reaction with carbon disulfide and aqueous ammonia,... 

When aryl acrylates and phenyl salicylates react with aliphatic aldehydes in the presence of DABCO, the normal Baylis-Hillman product (39) often reacts further to give the acetal (40) <96TL1715,96TL3755>. 

Besides the domino Michael/SN processes, domino Michael/Knoevenagel reactions have also been used. Thus, Obrecht, Filippone and Santeusanio employed this type of process for the assembly of highly substituted thiophenes [102] and pyrroles [103]. Marinelli and colleagues have reported on the synthesis of various 2,4-disubstituted quinolines [104] and [l,8]naphthyridines [105] by means of a domino Michael addition/imine cyclization. Related di- and tetrahydroquinolines were prepared by a domino Michael addition/aldol condensation described by the Hamada group [106]. A recent example of a domino Michael/aldol condensation process has been reported by Brase and coworkers [107], by which substituted tetrahydroxan-thenes 2-186 were prepared from salicylic aldehydes 2-184 and cycloenones 2-185 (Scheme 2.43). 

The interactions between the chiral Schiff bases being derivatives of 2-aminoalcohols and substituted salicylic aldehydes and titanium (IV) isopropoxide [33] have been monitored by aH NMR spectroscopy.81... 

The first use of room temperature ionic liquids as potential novel soluble phases for combinatorial synthesis has recently been described. As model reaction the Knoevenagel condensation of salicyl aldehyde grafted on to an imidazolium-derived ionic liquid was studied under the action of microwave irradiation (Scheme 12.19) [66]. Reactions were performed without additional solvent in the presence of a basic catalyst, utilizing microwave irradiation in a designated monomode microwave reac-... 

The possibility of carrying out a multistep synthesis makes it possible to obtain P,B-containing derivatives from unstable intermediate a-hydroxyalkylphosphines. Thus, phenylphosphine, salicylic aldehyde, phenylboric acid anhydride, and triethylamine interact to give a bicyc-lic product—2,8,9-trioxa-1 -borata-4-phospha-6,7 -benzobicyclo [3,3,3] nonane (115) [Eq. (74)] (87IZV2118 89IZV946). In this case an aldehyde takes part in the reaction opening up new synthetic possibilities. 

Analogous products have been obtained when salicylic aldehyde was replaced by o-hydroxynaphthaldehyde. 

The reaction of phenylphosphine with boric acid and 2 mol of salicylic aldehyde was carried out in the presence of pyridine with azeotropic removal of water and gave rise to the complex of pyridine with B(III) (116), bonded to three oxygen atoms (87IZV2118 89IZV946) [Eq. (75)]. 

More significant differences from the properties of cyclic boryloxyalkyl-phosphines were revealed for 5,6-benzo-4-diphenylphosphino-2-phenyl-l,3-dioxa-2-boracyclohexane (126), obtained by the interaction of diphe-nylphosphine, salicylic aldehyde, and phenylboric acid ester [Eq. (83)] (92IZV196). 

The stepwise condensation of 2-amino-5-ethyl-l,3,4-thiadiazole 83 with a mixture of salicylic aldehyde and acetylacetone in ethanol in a reagent mixture of 1 1 1 gave compound 84 in 36% yield <99RJOC624>. 

A similar coupling reaction of salicyl aldehydes with disubstituted alkynes, catalyzed by rhodium, is known... 

Hayashi et al.147 reported another highly enantioselective cyanohydrination catalyzed by compound 138. In this reaction, a Schilf base derived from fl-amino alcohol and a substituted salicylic aldehyde were used as the chiral ligand, and the asymmetric addition of trimethylsilylcyanide to aldehyde gave the corresponding cyanohydrin with up to 91% ee (Scheme 2-56). 

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