Condensation, of salicylaldehyde with

Method B involves the preparation of precursor of 2-alkyl-l-benzo-pyrylium salts, as shown in Scheme ll.50 2-Alkylbenzopyrylium salts have been prepared by condensation of salicylaldehyde with appropriate ketone in acetic acid or by alkylation or reduction of coumarin or chromone derivatives. Reaction of 2-alkylbenzopyrylium salts with salicylaldehyde gives directly a spirodibenzopyran or 2-vinynologue benzopyrylium salt 17 which then can be converted into the spirodibenzopyran by piperidine or pyridine. 

The Knoevenagel-type condensation of salicylaldehydes with malonic acid [14, 27], malonic ester [28], cyanoacetic ester [29], or Meldrum s acid [30], is... 

Benzo[h]furans have been formed by condensation of salicylaldehydes with a variety of esters of chloroacetic acids, in the presence of tetrabutyl ammonium bromide (TBAB), under the action of irradiation without solvent [86] (Scheme 8.61). 

The complexes CrL3, where LH is formed by condensation of salicylaldehyde with 2-furfurylamine or 2-thenylamine, contain the ligand in isomeric form (233).1118... 

Phenylcoumarins are conveniently prepared by the Knoevenagel condensation of salicylaldehyde with a benzyl cyanide, in the presence of base such as sodium hydroxide or piperidine, followed by acid hydrolysis of the resultant imine. A second convenient synthesis is via condensation of 2-methoxybenzaldehyde with benzyl cyanide and cyclization of the 2-methoxy-a-phenylcinnamic nitrile in pyridine (Scheme 12). 

Condensation of salicylaldehydes with 2-chloro-3-formylbutene and analogs gave 2-methylenechromcnc derivatives.227 The direct reaction of salicylaldehyde with 2-methyl-2-chlorobutane or 2-methylbutene with catalysts to give 2,2,3-trimethylchromene is reported in a patent228 The structure of the products from salicylaldehyde and dipheny-lenes229,230 has been revised, (see Section V,B).231... 

The use of complex aromatic a-haloketones affords special 2-aroyl-benzofurans, such as 263 (condensation of salicylaldehyde with 2-bromoacetylthianthrene)634 and 264 (condensation of salicylaldehyde with 2-bromoacetylbenzofuran).399... 

The related synthesis of benzopyrylium salts involves the condensation of salicylaldehydes with methyl ketones in a basic medium, which affords the unsaturated ketone (642). Cyclization occurs on treatment with acid. The same benzopyrylium salt is formed rapidly and in high yield if the condensation is effected under acidic conditions (Scheme 252) (73BSF3421). It has been proposed that the latter synthesis proceeds via an aldol condensation accompanied by the formation of a hemiacetal, followed by dehydration. 

The Schiff bases have contributed to a large extent to the development of the coordination chemistry of nickel(II), particularly those obtained by the condensation of salicylaldehyde with various mono- and poly-dentate amines. A large number of nickel(II) complexes have been synthesized with these ligands exhibiting all of the possible coordination geometries, spin states and spectromagnetic properties. The early complexes of nickel(II) with different salicylal-dimines have been covered extensively in a number of review articles.2246-2252... 

Schiff-base ligands prepared form the condensation of salicylaldehyde with diamines offer [N2O2] donor sets that are capable of coordinating a wide range of metals. Tin(IV) acetate reacts with salenH2 and R2SnCl2 reacts with either (3-MeO)salphen (R = Ph, Bu , or the ligand... 

The condensation of salicylaldehyde with malonic ester to give 2-carboethoxy-coumarin was carried out in absolute ethanol with addition of 4 ml. of piperidine and 0.5 ml. of acetic acid (refi. 3 hrs.). ... 

An extension to the range of metal-ion template reactions is provided by the condensation of salicylaldehyde with salicylaldehyde aminoquinazine which occurs... 

Scheme 5.8 Condensation of salicylaldehyde with diethyl-2-pentenedicarboxylate in the presence of MCM-41 OH1.

In the course of this reaction, derivatives of coumarin-3-carboxylic acid are produced. This synthesis proceeds under much milder conditions than the condensation based on the Perkin reaction which involves condensation of salicylaldehydes with acetic anhydride/acetate. 

Benzo[fo]furans have been formed by condensation of salicylaldehydes with a variety of esters of chloroacetic acids, in the presence of tetrabutylammonium bromide (TBAB), under the action of microwaves without solvent (Scheme 10.78) [152]. Potassium carbonate (20 mmol), TBAB (0.5 mmol), and salicylaldehyde derivatives (5.0 mmol) were mixed, and a chloroacetic ester (10 mmol) was then added dropwise. The mixture was stirred and then irradiated for 8 to 10 min. After extraction with CH2CI2 and evaporation, the products were purified by column chromatography. If an oil bath is used, full conversion of an aldehyde usually requires 3 h. 

Condensation of salicylaldehyde with malonic acid in the presence of montmorillonite KSF clay as a catalyst gave, under MWI for 12 min (Scheme 19),... 

The use of these intermediates to produce shikimates is shown in Figure 6.32. In principle, anethole (53) and estragole (methyl chavicol) (52) are available from phenol, but in practice, the demand is met by extraction from turpentine. Carboxylation of phenol gives salicylic acid (38) and hence serves as a source for the various salicylate esters. Formylation of phenol by formaldehyde, in the presence of a suitable catalyst, has now replaced the Reimer-Tiemann reaction as a route to hydroxybenzaldehydes. The initial products are saligenin (189) and p-hydroxybenzyl alcohol (190), which can be oxidized to salicylaldehyde (191) and p-hydroxybenzaldehyde (192), respectively. Condensation of salicylaldehyde with acetic acid/acetic anhydride gives coumarin (50) and 0-alkylation ofp-hydroxybenzaldehyde gives anisaldehyde (44). As mentioned earlier, oxidation of phenol provides a route to catechol (184) and guaiacol (188). The latter is a precursor for vanillin, and catechol also provides a route to heliotropin (61) via methylenedioxybenzene (193). 

Derivatives of 4-hydroxy-2-(trifluoromethyl)-4//-chromene 221 were obtained via condensation of salicylaldehydes with methyl ( -2-bromo-4,4,4-trifluoro-2-butenoate [111] or methyl 2-perfluoroaIkynoates [112], Treatment of 221 with Sarrett reagent in CH2CI2 generated chromones 220 in high yields [111]... 

Chizhov DL, Sosnovskikh VY, Pryadeina MV, Burgart YV, Saloutin VI, Charushin VN (2008) The first synthesis of 4-unsubstituted 3-(trifluoroacetyl)coumarins by the Knoevenagel condensation of salicylaldehydes with ethyl trifluoroacetoacetate followed by chromene-coumarin recyclization. Synlett 2008 281-285... 

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