With aromatic aldehydes

SchifT s reagent A solution of rosaniline in water decolorized with sulphurous acid. Aliphatic aldehydes and aldose sugars give a magenta colour with this reagent with aromatic aldehydes and aliphatic ketones the colour develops more slowly aromatic ketones do not react. 

The above are examples of the Claisen - Schmidt reaction. The formation of p-nitrostyrenes by reaction of nitroalkanes with aromatic aldehydes in the presence of aqueous alkali may be included under the Claisen- hmidt condensation ... 

Since pyridazinones are acidic compounds, they undergo IV-hydroxy- and N-amino-methylation. They react also with aromatic aldehydes in the presence of acetic anhydride in the ratio of 2 1 to give the condensation product (73 Scheme 23). 

Both 2- and 3-methyl groups in pyrido[2,3-Z ]pyrazines are acylated by ethyl oxalate (71TH21500). They give (preferentially 3-) styryl derivatives with aromatic aldehydes and oximes with pentyl nitrite. 

The a-ionization of 7-methylpteridines can also be utilized in aldol-type condensation reactions. 7-Methyl-pterin and -lumazine and 2,4-diaminopteridine condense readily in aqueous base with aromatic aldehydes to afford 7-alkylidenepteridines (77JOC2951). A Claisen condensation requires the protection of the acidic hydrogens of the amide bonds. 

The stabilized phosphonium ylide (601) reacts with aromatic aldehydes to give N-phenacylpyrazoles (602) in good yields (73CC7). Ketone semicarbazones and ketazines react with two moles of phosphorus oxychloride-DMF, the Vilsmeier-Haack reagent, with the formation of 4-formylpyrazoles (603 R = H or PhC=CH2) (70JHC25, 70TL4215). 

Toward the end of the 19 century both Pomeranz and Fritsch independently reported the preparation of isoquinolines by the reaction of aminoacetaldehyde dimethyl acetal 2 (R = Me) with aromatic aldehydes 1 followed by cyclisation in acidic media. " Unfortunately yields were often poor and not always reproducible. This has prompted the search for various improvements and modifications on the original theme, including the use of reagents other than strong mineral acid which tends to destroy the intermediate imine. ... 

The reactivity of 1-methyl groups is further exemplified by their facile reaction with aromatic aldehydes to... 

Cyclization of the 3-(2-aminoethyl)-l,2,4-triazoles 60 with aromatic aldehydes gave a mixture of the corresponding Schiff bases 61 and the 5,6,7,8-tetrahydro-l,2,4-triazolo[l,5-c]pyrimidines 62. Cyclization of 60 with car-bonyl-1,1 -diimidazole (CDI) afforded the 5-oxo analogs 63 (92JPR630) (Scheme 22). 

Heating the mesoionic l-amino-2-thioxo-l,2,4-triazolo[l,5-c]quinazo-lines 59 with aromatic aldehydes and ethanolic hydrochloric acid resulted in the formation of Schiff bases and simultaneous pyrimidine ring cleavage... 

A series of 2-aryloxazolo[4,5-/i]quinoline-5-arylidines was prepared by the reaction of 5,7-diamino-8-hydroxyquinoline with aromatic or aliphatic aldehydes in the presence of a basic catalyst such as piperidine. On the other hand, 2-styryl-5-diacetylamino-oxazolo[4,5-/i]quinolines were prepared by interaction of 2-methyl-5-diacetylamino-oxazolo[4,5-/i]quinoline with aromatic aldehydes (77MI1, 82MI2) (Scheme 6). 

A novel method of forming 2-aryl derivatives of 5,6-dihydro-1,3-4H-oxazine (35) consists in reacting 3-azidopropanol with aromatic aldehydes/ ... 

Further, isoxazole derivatives were subjected to two related reactions. 3,5-Dimethylisoxazole was found to react in the presence of dry hydrogen chloride with aromatic aldehydes (chlorobenzylation, 72- 71),and with formaldehyde in the presence of sulfuric acid it undergoes hydroxymethylation (72- 73). ... 

Good yields are usually obtained with aromatic aldehydes or ketones. Aliphatic aldehydes are poor substrates for the ordinary procedure, but react much better if the halo ester is first deprotonated with lithium diisopropylamide (LDA) in tetrahydrofuran at -78 °C, prior to addition of the aldehyde. 

A primary or secondary amine can be used, as well as ammonia. With respect to the carbonyl component used, the best results have been obtained with aromatic aldehydes and with high boiling ketones. 

The preparative value of this compound lies in the surprising fact that bis(l,3-diphenylimidazolidinylidenc-2) behaves in many reactions ie.g., with aromatic aldehydes,2,7 and with carbon acids 2 7-fJ) as if it dissociated to form a nucleophilic carbene. The hydrolytic cleavage of these derived imidazolidine derivatives makes possible the preparation of formyl compounds, so that the amino olefin can be considered as a potential carbonyla-tion reagent. In many reactions it is not necessary to isolate... 

Benzodiazepinones condense with aromatic aldehydes under basic conditions to form 3-arylidcne compounds 36.281 306... 

Condensation of 1,3-diphenyl[ 1,2,4]triazin-6-one 360, obtained from reaction of hippuric acid and phenylhydrazine, with aromatic aldehydes... 

The reported examples of ring system 593 were prepared by heating l-amino-3-alkylbenzimidazolium iodides 592 with aromatic aldehydes in polar aprotic solvents to give 593 via intermediate Schiff bases (86KGS346) (Scheme 122). 

Thiazolotriazines 636 (R = CO,Me) were prepared [84JCS(P1)2707] by cycloaddition of dimethyl acetylenedicarboxylate with triazine derivative 632. Derivatives of thiazolo[3,2-b][l,2,4]triazin-3,7-diones 637 have been formed (74JPR163) on reaction with aromatic aldehydes and diazonium salts to give 636 (R = Ar) and 638, respectively. Regioselective catalyzed... 

The sequential treatment of triazine derivative 990 with acyl chlorides and acetic anhydride and perchloric acid afforded (86H1031) thiadi-azolo[l, 2,4]triazinium perchlorates 991. On the other hand, cyclocondensation of 992 with organic acids gave 993 [82JHC1577 83JAP(K)58/180492] and 994 with aromatic aldehydes (84JIC552) (Scheme 183). 

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