With salicylaldehyde

The DOOB reagent, which is formed by reaction of diphenylboric anhydride with salicylaldehyde, yields fluorescent reaction products with primary amines [1]. 

Amino acids were protected by reductive alkylation with salicylaldehyde (NaBH4, KOH, aq. EtOH). The amine is released by treatment with CF3SO3H (TFA, EDT, PhSMe, 2 h, >75% yield). ... 

Comforth has reviewed literature reports and independently studied the special cases of reaction of 1 with salicylaldehyde and with 2-acetoxybenzaldehyde. Coumarins (10) are afforded in the condensation of 1 with salicylaldehyde or its imine, whereas when 2-acetoxybenzaldehyde is used, acetoxy oxazolone 12 is the major product. The initial aldol condensation product between the oxazolone and 2-acetoxybenzaldehyde is the 4-(a-hydroxybenzyl)oxazolone 11, in which base-catalyzed intramolecular transacetylation is envisioned. The product 9 (R = Ac) can either be acetylated on the phenolic hydroxy group, before or after loss of acetic acid, to yield the oxazolone 12, or it can rearrange, by a second intramolecular process catalyzed by base and acid, to the hydrocoumarin, which loses acetic acid to yield 10. When salicylaldehyde is the starting material, aldol intermediate 9 (R = H) can rearrange directly to a hydrocoumarin. Comforth also accessed pure 4-(2 -hydroxyphenylmethylene)-2-phenyloxazol-5(4//)-one (13) through hydrolysis of 12 with 88% sulfuric acid. 

Demailly and coworkers195 found that the asymmetric induction increased markedly when optically active methyl pyridyl sulfoxide was treated with an aldehyde. They also synthesized (S)-chroman-2-carboxylaldehyde 152, which is the cyclic ring part of a-tocopherol, by aldol-type condensation of the optically active lithium salt of a,/3-unsaturated sulfoxide. Although the diastereomeric ratio of allylic alcohol 151 formed from lithium salt 149 and 150 was not determined, the reaction of 149 with salicylaldehyde gave the diastereomeric alcohol in a ratio of 28 72196. 

Bis(alkylsulfonyl)methanes361,363 or bis(phenylsulfonyl)methane362 readily reacted with aldehydes in the presence of bases to afford /1-hydroxysulfones or bis-adducts. For example, bis(ethylsulfonyl)methane was found to react with salicylaldehyde in the presence of piperidine, affording 2-ethylsulfonylbenzofuran in a good yield363. 

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. 

H2acac2trien of triethylenetetramine with salicylaldehyde Schiff base obtained from the 1 2 condensation... 

In a systematic study of the effects of variation of the tetramine involved in formation of the hexadentate N402 donor Schiff base the linear 3,3,3-, 3,2,3-, 2,3,2- or 2,2,2-tetramines, where the numbers refer to the number of carbon atoms between the amine groups (note 2,2,2-tetramine is synonymous with the nomenclature trien used previously) have been condensed with salicylaldehyde, acetophenone or benzophenone [206]. Crystal struc-... 

Aromatic aldehydes react with primary amines forming Schiff s bases which are often coloured. The colour may then be used to quantitate the amine. Using this principle Kocyl has shown neomycin to form a yellow-coloured Schiff s base with salicylaldehyde though the quantitative aspect of this procedure is, as yet, incomplete. 

Using the tandem aza-Wittig/bir-electrocyclization strategy, an isoquinoline synthesis starts with salicylaldehyde, which is converted with azido-... 

Hydrazine may be derivatized with salicylaldehyde to a hydrazone derivative, separated on a suitable HPLC column and determined by a UV detector. Aqueous samples may be directly injected into a polar GC column interfaced to an FID. Anhydrous hydrazine may be appropriately diluted in alcohol or ether and determined by GC/MS. The molecular ion for GC/MS determination by electron-impact ionization is 32. 

The system Ru(PPh3)(H20)2(SB )/Phl0/CH3Cy4°C asymmetrically epoxidised styrene [917]. Related complexes made from L-histidine with salicylaldehyde, 5-chloro and 5-methoxysalicylaldehyde as Ru(PPh3)(H30)3(SB )/(PhIO/CH2Cl2 epoxidised non-functionalised styrenes at unspecified low temperatures in the dark. Possible mechanisms were discussed [918]. 

Spiro tetrahydroquinoxaline-2,2 -[l]benzopyran (247) has been obtained from l,2,4-trimethyl-3-oxo-3,4-dihydroquinoxalinium metho-sulfate with salicylaldehyde.239... 

Ethyl cyanoacetate in the presence of piperidine may also be used as the carbanionic component in reactions with salicylaldehyde. The initial Knoevenagel condensation is followed by a [l,7]-sigmatropic shift and cyclization to the 2-iminochromene derivative which adds another cyanoacetate molecule (67AP1). 

Keto esters also react with salicylaldehyde to yield fused pyrylium salts. For instance ethyl 2-oxocyclohexanecarboxylate affords the tetrahydroxanthylium salt (645), whilst the isochromanone derivative (646) yields the tetracyclic molecule (647), which possesses the skeleton of the anthocyanidin, peltogynidine, isolated from the heartwood of Peltogyne porphyrocardia (Scheme 253) (58JCS3174). 

The reaction of the dimethyl acetal of phenylacetaldehyde with salicylaldehydes enables 3-phenylbenzopyrylium salts to be prepared (82JHC97) and the reaction of arylmalondial-dehydes with phloroglucinol provides another variation on this theme which also affords isoflavylium salts (81AJC2647). 

A charge-transfer complex [ZnLQ] (H2L = 28 Q = p-chloranil) has been characterized, and a weak n-n interaction between the ZnL and Q moieties demonstrated.338 A related complex, [ZnL] (H2L = 29), is formed from the template condensation of HCN tetramer, H2N(NC)C=C(CN)NH2 with salicylaldehyde in the presence of ZnCl2.339 In the absence of the zinc salt, unsymmetrical mono-Schiff bases are obtained. 

The reaction of picolinoylhydrazide with salicylaldehyde results in the formation of the ligand (73), which may act as a bi-, ter- or quater-dentate donor, and a number of zinc complexes of this ligand have been prepared.530... 

It is well over 40 years since Pfeiffer discovered that certain reactions of a-amino acid esters, in particular, ester exchange, racemization and oxygenation, are effected very readily when their Schiff bases with salicylaldehyde are complexed to a transition metal ion (most notably Cu11). The Schiff bases result from a condensation reaction between a reactive carbonyl group and the amino group of the amino acids. Snell and his co-workers43 were also one of the first to point out that similar reactions also occurred if pyridoxal was used instead of salicylaldehyde, and that there is a close analogy with pyridoxal phosphate-promoted enzymic reactions of a-amino acid metabolism. Since then much work has been due on these and other similar systems and their reactivities. 

The experiments showed that the derivatives were stable under refrigeration for at least 1 week (73), and they were stable at room temperature up to 48 hours (76). This analytical procedure is superior in terms of selectivity and sensitivity. The main disadvantage is that it is suitable for the analysis of am ino-/3-lac tarns only. No fluorescent derivatives were formed when other common /3-lactam antibiotics were treated with salicylaldehyde or formaldehyde (76). 

A kinetic study of the Schiflf base condensation of m-toluidine with salicylaldehyde has examined the effects of proton, hydroxide, general base, and transition metal catalysts, and also solvent effects.25... 

Scheme 4 Imprinting approach used by Wulff et al. for the preparation of a polymer capable of performing enantioselective synthesis. The l-DOPA (16) is reacted with salicylaldehyde (17) to give the corresponding Schiff s base (18) that reacts with borane (19) to generate the imprinting complex (20)...

Base-catalyzed condensation (Equation 31) of 4,6-dinitro-l-tosylindoline with salicylaldehyde or 2-hydroxy-naphthalene-l-carbaldehyde is accompanied by intramolecular nucleophilic substitution for one of the nitro groups to give benzo- and naphthooxepino[4,3,2-crf indoles, respectively <2003IZV725>. 

Figure 4-22. The imine formed from the reaction of 1,2-diaminoethane with salicylaldehyde is stable to hydrolysis.

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