Aldehydes, condensation with

Aldehydes condense with alcohols in the presence of a catalyst (1-2-5 per... 

Claisen-Schmidt reaction. Aromatic aldehydes condense with aliphatic or mixed alkyl-aryl ketones in the presence of aqueous alkali to form ap-unsaturated ketones ... 

Chloro-a,/3-unsaturated aldehydes condense with ammonium thiocyanate to give isothiazoles (76EGP122249). 2,3-Diphenylcyclopropenone reacts with iV-sulfinyl-cyclohexylamine in the presence of nickel tetracarbonyl to give the isothiazolin-3-one 1-oxide (197) (79SST(5)345). Cholesteryl acetate reacts with trithiazyl trichloride in pyridine to give the isothiazolo steroid (198) (77JCS(P1)916). 

Aliphatic and aromatic aldehydes condensed with 2-amino-(62BRP898414), 5-amino- (80AJC1147), or 8-amino-l,2,4-triazolo[l,5-cjpyrimidines (68JOC530) to give the related Schiff bases. Treatment of the 2-amino-5-methyl-l,2,4-triazolo[l,5-c]quinazoline 11 with formaldehyde and piperidine in the presence of acetic acid gave the 2-hydroxymethyl-amino-5-(2-piperidinoethyl) derivative 172. Utilization of aromatic aldehydes and piperidine in this reaction gave the 2-arylideneamino-5-styryl derivatives 173 (68CB2106) (Scheme 67). 

Pyruvic Acid Compounds.—Lubrzynska and Smedley have recently shown that a number of aldehydes such as heliotropin, anisic aldehyde, benzaldehyde, and cinnamic aldehyde, condense with pyruvic acid in slightly alkaline solution, with the formation of )8-unsaturated-a-ketonic acids. For example, if heliotropin and pyruvic acid in alkaline solution be left standing for about eight days at ordinary temperature, dihydroxy-methylene-benzal-pyruvic acid is formed. This body forms yellow needles, melting at 163° Similarly, anisic aldehyde yields methoxy-benzal-pyruvic acid, melting at 130° and cinnamic aldehyde yields cinnamal-pyruvic acid, melting at 73°. 

Aldehydes condense with compounds containing a reactive methyl-or methylene-group to form unsaturated ketones, e.g. 

A. The Basic Series.—In general, aromatic aldehydes condense with aromatic amines in the presence of zinc chloride to form triphenylmethane derivatives (0. Fischer) phenols and phenyl ethers behave similarly in the presence of concentrated sulphuric acid (Baeyer). The products formed are the leuco-compounds of well-known dyes. 

Aldehydes condense with DISN to give 2-alkylimidazoles, but in low yield (73USP37099(X)). A related reaction with ketones produces 2,2-dialkyl-4,5-dicyano-2//-imidazoles. When one alkyl group is methyl and the other is a... 

Aliphatic and aromatic aldehydes condense with aliphatic and aromatic primary amines to form JV-substituted imines. The reaction is catalyzed by acids and is generally carried out by refluxing the amine and the carbonyl compound with an azeotroping agent in order to separate the water formed. The aliphatic imines (C5-C10) are obtained in good yield but are unstable and must be used directly after their distillation [2b], Tertiary aliphatic and aromatic aldehydes at room temperature react readily and nearly quantitatively with amines to give the imines without the aid of catalysts [la]. Primary aliphatic aldehydes tend to give polymeric materials with amines as a result of the ease of their aldol condensation [3]. The use of low temperatures and potassium hydroxide favors the formation of the imine product [4a, b]. Secondary aliphatic aldehydes readily form imines with amines with little or no side reactions [5]. 

The aldol-type reaction of a cyclic enol ester, 5-methyl-2(3//)-furanone (4b), was carried out with three kinds of catalytic systems PdCl2 (PhCN)2-SnCl2, Ni(Cod)2/Ph3P-Zn, and Pd(OAc)2/PPh3-Zn. In the presence of the first catalyst, aromatic aldehydes condense with 4b to give ds-)3-acetyl-y-aryl-y-butyrolactones (47), but alkanals are mainly con-... 

A retrosynthetic analysis of a,/J-unsaturated ketones leading to various methods of synthesis is outlined in Section 5.18.2, p. 798. These methods are equally applicable to aromatic aldehydes. Aromatic aldehydes condense with aliphatic or mixed alkyl aryl ketones in the presence of aqueous alkali to form a,[i-unsaturated ketones (the Claisen-Schmidt reaction). 

In the Vilsmeier formylation of iV-( 3-hydroxyethyl)anilines the hydroxyl group is simultaneously replaced by chlorine [60], The resulting aldehydes condense with l,3,3-trimethyl-2-methyleneindoline to form very brilliant dyes [61], With 4-(W-methyl-iV- 3-chloroethylamino)benzaldehyde a commercial dye is obtained. A methyl group in the 2-position to the methine chain produces a bluish-red color (27). 

Aromatic aldehydes condense with phenols, e. g. benzaldehyde and naphthol give hydroxy-dinaphthyl-phenyl methane ... 

When aldehydes condense with 2-amino-2-phenylacet-amidoxime (23) derivatives of 5-aminoimidazole (24) are formed in high ( 80%) yield.112... 

Both aliphatic and aromatic aldehydes condense with primary amines, aliphatic and aromatic, to form N substituted imines. The purely aliphatic imines (C, to C,) can be obtained in 50 80% yield however, these compounds are unstable and should be used immediately after distillation. ... 

Simple saturated and olefinic aldehydes condense with ammonia to give alkylpytidines (Chichibabin), but the products are frequently complex mixtures from which pure compounds are separated with difficulty. An exception is the preparation of 5-ethyl-2-methylpyridine in 53% yield from paraldehyde and ammonium hydroxide. In an extensive study of the reaction, it has been pointed out that other single products can sometimes be obtained in fair yields by proper choice of reagents and conditions. ... 

Dialkylamino aldehydes condense with Grignard reagents to give dial-kylamino alcohols ... 

Reactions of piperazine-2,5-diones with phosphorus pentachloride and phosphorus pentabromide have been described in Sections V.ID and V.IF, respectively. Aromatic aldehydes condense with 3-methylpiperazine-2,5-dione in the presence of acetic anhydride to form mainly mono-A -acetyl derivatives of trans-3-arylidene-6-methylpiperazine-2,5-diones (e.g., 96, R = Ac) (1066). In these products the acetyl group was shown to be attached to position 1 and the 4,5-amide group was found to be sterically hindered. Photolysis formed the cis isomers. Both isomers were deacetylated with methanolic potassium hydroxide (1066). Condensation of 1,4-diacetylpiperazine-2,5-diones with aldehydes has been applied to the synthesis of unsymmetrical 3,6-diarylidenepiperazine-2,5-diones and the reaction has been extended to l,4-diacetyl-3,6-dimethylpiperazine-2,5-diones (1624). Treatment of (96, R = H) with triethyloxonium tetrafluoroborate in dichloromethane gave the monoimino ether, 5-benzylidene-6-ethoxy-3-hydroxy-2-methyl-2,5-dihydropyrazine (97) (1066). l-Methylpiperazine-2,5-dione similarly treated gave 5-ethoxy-l-methyl-2-oxo-l,2,3,6-tetrahydropyrazine (which was condensed with anthranilic acid at 150° to 2-methyl-l,2-dihydropyrazino[2,l-fi]quinazoline-3(4/0.6-dione (98) (1625), and l,4-dimethylpiperazine-2,5-dione gave 5-ethoxy-l,4-dimethyl-2-oxo-1,2,3,4-tetrahydropyrazine and 5,5-diethoxy-l,4-dimethylpiperazin-2-one (1626). 

Aryl aldehydes condense with aliphatic aldehydes in the presence of benzoylfor-mate decarboxylase and thiamin diphosphate to give an a-hydroxy ketone with god enantioselectivity. ° ... 

Color test for pyrroles. One drop of an aqueous, ethereal, or alkaline test solution is mixed on a spot plate with one or two drops of a 5% solution of p-dimethylamino-benzaldehyde. If pyrrole or a substance capable of forming pyrrole is present, a violet color will appear. The aldehyde condenses with a tautomeric form of pyrrole (3) to give (4), which is converted by hydrogen ion into the colored quinonoid ion... 

The Erlenmeyer azalactone synthesis generally affords predominantly, and often exclusively, (Z) isomers (32). However, a simple method for the synthesis of ( ) isomers (33), obtained previously by separation of isomeric mixtures or isomerization procedures, has been reported. Aromatic aldehydes condense with hippuric acid when heated in polyphosphoric acid (PPA) to afford (33) in 80-90% yields (equation 17 Table 4). Alternatively, the (Z) isomers may be heated in PPA to afford the corresponding ( ) isomers in excellent yield. The authors note that hippuric acid is not converted to (26) in PPA, the generally accepted intermediate in the Erlenmeyer synthesis. Furthermore, both isomers of 2-(benzamid-oyl)cinnamic acid, (34) and (35), obtained by the alkaline hydrolysis of (32 R = H, Ar = Ph) and (33 R = H, Ar = Ph), respectively are converted to (33 R = H, Ar = Ph) in PPA (Scheme 9). The authors therefore suggest a mechanism involving condensation, first of the aldehyde and hippuric acid followed by... 

---