Malononitrile condensation with

Malononitrile condenses with 3-pyridinecarboxaldehyde and a ketone to form substituted bipyridine (6) (Scheme 4) <95JCR(S)(4)146>. 

Multicomponent one-pot reactions continue to be the focus of heterocyclic synthesis when multi-bonds are formed. Malononitrile condenses with 3-pyridinecarbaldehyde and a ketone to form a substituted bipyridine (Equation 179) <1995JCM146>. In another condensation, with aniline being the ultimate source of the tetrahydroquinoline nitrogen atom, iodine is used as a catalyst in a reaction that was optimized for yield and diastereoselectivity (Equation 180) <2005SL2357>. 

The only acid-resistant protective group for carbonyl functions is the dicyanomethy-lene group formed by Knoevenagel condensation with malononitrile. Friedel-Crafts acylation conditions, treatment with hot mineral acids, and chlorination with sulfuryl chloride do not affect this group. They have, however, to be cleaved by rather drastic treatment with concentrated alkaline solutions (J.B. Basttis, 1963 H. Fischer, 1932 R.B. Woodward, 1960, 1961). 

When the NHx surface groups (Table 1) are only considered, a good correlation with the malononitrile condensation is obteiined (Figure 3). 

The thiadiazolo[3,4-g] indole 100 was prepared from 4-amino-5-chlorobenzothiadiazole 99 by treatment with pyruvic acid in the presence of [Pd(But3P)2] (Equation 14) <2004AGE4526>. The Herz reaction of 4-aminoben-zothiadiazole 101 with disulfur dichloride gave the fused 1,2,3-dithiazolium chloride 102, which was condensed with malononitrile to give the ylidene 103 (Scheme 15) <2002J(P1)315>. 

Numerous solvent-free Knoevenagel condensations with malononitrile, methylcyanoacetate, dimedone (255), and Meldrum acid proceeded with high to quantitative results with intermediate melt or full melt at higher temperatures but with direct crystallization [107]. 

Aminopyrimido[4,5-d]pyrimidine (124) undergoes an interesting rearrangement to the pyridopyrimidine (129) when condensed with malononitrile in glacial acetic acid... 

The most popular preparations of pyrimido[4, 5 ]pyrimidi nes are based on cyanoethylene or cyanomethylene derivatives. In many of these preparations the appropriate acid chloride (R1 = alkyl, aryl) is reacted with malononitrile to give an enol (250), which is readily alkylated to the enol ether (251). This can be condensed with guanidine or a variety of amidines (R2 = H, alkyl, aryl) to yield the key intermediate 4-amino-5-cyanopyrimidines (252) (81S955). Reaction with a second mole of guanidine or amidine is a convenient preparation of a variety of pyrimido[4,5 ]pyrimidines. Under the appropriate conditions the final ring system can be obtained from the enol ether in one step (68JMC568). 

Benzo[6]thiophene aldehydes have been condensed with a variety of active methylene compounds, including cyclic511, 644 and open-chain645-647 ketones, aliphatic aldehydes,90 benzyl cyanides,93-436 malononitrile,487 rhodanine,144,648 hippuric acid,477 barbituric acid,487 diethyl malonate,487 and malonic acid (Section VI,M). Aliphatic nitro compounds condense smoothly with most benzo[6]-thiophene aldehydes03,141,337,343, 556,640,650 (except 5-hydroxy- and... 

Compound 98 was condensed with o-aminothiophenol, 2-aminoethanol, or cystamine in refluxing diphenyl ether through an intermolecular cyclization with the elimination of two molecules of water to give the polyfused derivatives 101-103, respectively. Also, the reactions of 98 with dimethylthiomethylenemalononitrile in boiling dimethylforma-mide (DMF) were studied. The dimethylthiomethylenemalononitrile was prepared via the reaction of malononitrile with CS2 with 2 equiv of methyl iodide in a one-pot reaction using liquid-liquid phase-transfer catalysis (PTC) technique (NaOH/dioxane/tetrabutylammonium bromide (TBAB)). The product of this reaction was identified as 8-cyano-9-imino-7-methylthio-6-oxo-3-phenyl-5,6,8,9-tetrahydro-77/-pyrano[3,2-/][l,2,4]-triazolo[3,4-A][l,3,4]thia-diazepine 104 (Scheme 10). 

A three-component reaction of aromatic aldehydes, malononitrile and phenols leads to 4-aryl-2-amino-3-cyano-4//-chromenes this reaction can be carried out in aqueous media with improvements in yield and obvious environmental advantages (Scheme 35). The aromatic aldehyde undergoes a Knoevenagel condensation with malononitrile, followed by ortho-alkylation of the phenol and cyclization to form the iminopyran intermediate 114, which isomerizes to the 4//-chrorncncs (Scheme 36) <2003SL2001>. High yields for this three-component reaction can also be achieved in aqueous media when mediated by 7-alumina <2004TL2297> or cetyltrimethylammonium chloride <2001T1395>. 

In the presence of morpholine and malononitrile, the initial reaction of cyclohex-3-enal with cyanothioacetamide is followed by a condensation with the dinitrile. Cyclization follows through attack of the thiol on a nitrile function and a penta-substituted 477-thiopyran is formed (Scheme 126) <1998RJ0557, 2005RJC1537>. 

Disubstituted and unsubstituted l,2,5-thiadiazolo[3,4- ]quinoxaline-4,9-diones (110) have been prepared in good yield by condensation of 5,6-diaminobenzo[c][l,2,5]thiadiazole with a-dicarbonyl reagents (Equation (62)) <92H(33)337>. These quinones were then converted into 1,2,5-thiadiazolo-, pyrazino-fused TCNQ analogues by condensation with malononitrile in the presence of TiCl4 in dry pyridine. The x-ray crystal structure determination of the product derived from compound (110 R1 = R2 = H) has been accomplished. 

Thiohydantoins undergo ready condensation with a,j6-unsaturated nitriles to give pyrrolo[l,2-c]imidazoles (equation 27). The same products were obtained when the corresponding 5-methylene-2-thiohydantoins were treated with malononitrile (82S502). A likely pathway has been suggested (81S531). 

The employment of activated cyanomethylene compounds (e.g., malononitrile) for condensation with -amino carbonyl derivatives (e.g., the protected aminoacetaldehyde 184) provides 2-aminopyrroles 185 (Scheme 101) <2004OL2857>. In a comparable fashion, the condensation of -mercapto carbonyl compounds with malononitrile derivatives provides 2-aminothiophenes (Scheme 102) <1979LA328>. Similarly, 2-aminofuran-3-nitriles can be obtained by base-catalyzed condensation of -hydroxy ketones with malononitrile < 1966GB 1002>. 

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