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Aldehydes 5- aryl oxazoles

The tosyl compound reacts with aldehydes in the presence of potassium carbonate to yield 5-alkyl- or 5-aryl-oxazoles, the intermediate dihydrooxazoles (which can be isolated) eliminating toluene-p-sulfinic acid (Scheme 30). Use of acyl chlorides in place of aldehydes leads to 4-tosyloxazoles (288). Furthermore, alkylation of tosylmethyl isocyanide with an alkyl halide RfX, followed by treatment with an aldehyde R2CHO, yields a 4,5-disubstituted oxazole (289). A related reaction is that of A-tosylmethyl-iV -tritylcarbodiimide with aromatic aldehydes under phase-transfer catalysis to yield 2-tritylaminooxazoles which are readily converted into 2-amino-5-aryloxazoles (equation 117) (81JOC2069). [Pg.220]

Moreover, aryl-oxazoles, -imidazoles [17], or-thiazoles [18], anhydrides [19], and imides [20] are accessible via intramolecular Heck-type carbonylations. In addition to typical acid derivatives, aldehydes [21], ketones [22], aroyl cyanides, aroyl acetylenes, and their derivatives [23] could be synthesized via nucleophilic attack of the acyl metal complex with the corresponding hydrogen or carbon nucleophiles. Even anionic metal complexes like [Co(CO)4] can act as nucleophiles and lead to aroylcobalt complexes as products [24]. [Pg.147]

PS-p-toluenesulfonylmethyl isocyanide (TosMIC) reagent, developed by Barrett et al. was found to be effective for the conversion of a range of aryl aldehydes into highly pure 4-aryl oxazoles in the presence of BTMG (2) [79] (Scheme 4.29b). A typical procedure involved the reaction of aldehyde with the gel (4 equiv.) in acetonitrile (0.2M sol) and BTMG (2) (4 equiv.) for 12 h at 65 °C. ... [Pg.118]

The anions of 2-(arylsulfinylmethyl)oxazoles can be added to aldehydes to give 2-(l-aryl-sulfinyl-2-hydroxyalkyl)oxazoles which have been transformed into /1-hydroxy acids. With lithium bases, the enantioseleetivity could be increased to 50%. The use of a more chelating counter ion, such as magnesium, lowered the optical yields44. [Pg.661]

Monosubstituted and 4,5-disubstituted oxazoles were easily obtained from aryl-substituted tosylmethyl isocyanides and aldehydes . Tosyloxazoles 107, prepared from TosMIC 106 and carboxylic acid chlorides, led to 5-substituted derivatives 108 through ultrasound-promoted desulfonylation <00JCS(P1)527>. [Pg.224]

The condensation of furo[3,2- ]pyrrole-type aldehydes 8g and 265-267 with hippuric acid was carried out in dry acetic anhydride catalyzed by potassium acetate as is shown in Scheme 26. The product methyl and ethyl 2-[( )-(5-oxo-2-phenyl-l,3-oxazol-5(4//)-ylidene)methyl]furo[3,2- ]pyrrol-5-carboxylates 268a-d were obtained. The course of the reaction was compared with the reaction of 5-arylated furan-2-carbaldehydes with hippuric acid. It was found that the carbonyl group attached at G-2 of the fused system 8 is less reactive than the carbonyl group in 5-arylated furan-2-carbaldehydes in this reaction <2004MOL11>. The configuration of the carbon-carbon double bond was determined using two-dimensional (2-D) NMR spectroscopic measurements and confirmed the (E) configuration of the products. [Pg.30]

The oxazoles and their derivatives have played a variety of fascinating roles in the preparation of new molecular systems. Much of this chemistry stems from their ability to serve as diene components (azabutadiene equivalents) in reactions with a variety of dienophilic agents, to undergo nuclear metallation, to activate attached aryl or alkyl groups to deprotonation (thus functioning as masked aldehydes, ketones or carboxylic acid groups), and to serve as useful electrophiles on conversion to AT-alkylated salts. [Pg.444]

Aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]-quinazolines Isatoic anhydride could also be reacted with amino-, hydroxyl- or thiolanilines to form 2-(2-aminophenyl)benz-imidazoles, oxazoles or thiazoles, Scheme 5.38. In the case of 2-(2-aminophenyl)benzimidazoles (X=N), the product was formed after 3 min at 150°C in acetic acid. The products could subsequently be further elaborated 6-aryl-5,6-dihydrobenzo[4,5]imidazo[l,2-C]quinazolines, a four ring system, was formed by treatment of the 2-(2-aminophenyl) benzimidazole (X=N) with different aldehydes in acetic acid at 150°C for 5 min (J. Westman, and K. Orrling, Personal Chemistry, Uppsala, Sweden, unpublished results). Fifteen compounds were synthesised in 20-75% overall yield. This 3 + 5 min procedure should be compared to the conventional heating protocol developed by Devi and co-workers57, where each reaction step was run overnight to eventually afford the products in only 30-50% yield. [Pg.128]

The reaction of -halo carbonyl compounds with primary amides is appropriate for oxazoles containing one or more aryl groups . Ureas form 2-aminooxazoles. Formamide can be used resulting in a free 2-position in the oxazole. A convenient synthesis of 5-substituted-4-cyanooxazoles 223 is based on the condensation of -hydroxy—cyanoenamines 222 with trimethyl orthoformate (Scheme 109). The cyanoenamine intermediates 222 are derived from Lewis acid-catalyzed Passerini reactions between /-butyl isonitrile and aldehydes <2002S1969>. [Pg.736]

Oxazoles can react at the C-4 position with aromatic aldehyde electrophiles under Friedel-Crafts conditions when the C-5 position is substituted with an alkoxy group. This feature has been exploited in a chiral Lewis acid-catalyzed formal [3-1-2] cycloaddition of aromatic aldehydes and 2-aryl-5-methoxyoxazoles 45 to generate enantiomerically enriched 2-oxazoline-4-carboxylates 46 (Scheme 4) <2001AGE1884>. These products can serve as masked /3-hydroxy a-amino acids, which are useful synthetic intermediates and have been found in peptide-based natural... [Pg.494]

The reaction of aryl aldehydes with benzotriazol-l-ylmethyl isocyanide (154), obtained in two steps from benzotriazole, formaldehyde and formamide, gives 5-aryl-substituted oxazoles in 35-69% yields (Scheme 71) <89TL6657>. [Pg.302]

Some multicomponent syntheses of trisubstituted oxazoles were described. a-Isocyano-a-alkyl(aryl)acetamides, as 131 <05S161>, was demonstrated to be a useful starting material for a three-component reaction involving isoquinoline 129 <05SL532>. A four-component synthesis was also published starting from an aldehyde, a silylamide, an acyl chloride and a terminal acetylene derivative. The overall process is a modification of a four-component synthesis of a propargylic amide 134 which can be eventually isolated <05T 11317>. [Pg.299]

Condensation of a-phenyl-a-acylaminoacetonitriles with aromatic or aliphatic aldehydes by heating at 140° in the presence of zinc chloride, or by treatment in alcohol or chloroform with dry hydrogen chloride, produces Schiff bases of 2-aryl (or alkyl )-4-phenyl-5-aminooxazoles.205 The reaction of benzaldehyde with benzene sulfonamide and potassium cyanide (molar ratio 1.0 0.33 0.2-0.25) at 135° gives a 9-22% yield of 2,4-diphenyl-5-(benzylideneamino)oxazole and has been proposed to proceed through a-benzoylaminophenylacetonitrile.206... [Pg.151]

Hojo and co-workers " described a novel synthesis of 4-aryl-5-(trifluoro-methyl)oxazoles 331, starting from aldehyde tert-butyl(methyl)hydrazones (Scheme 1.89). Triiluoroacetylation of a tert-butyl(methyl)hydrazone 327 yields 328 that cyclizes to a 4,5,5-trisubstituted oxazoline 329 upon refluxing in toluene in the presence of silica gel. Dehydration of 329 was then accomplished in two steps using POCI3 and a base to generate the 4-aryl-5-(trifluoromethyl)oxazoles 331. [Pg.71]

TABLE 1.26. 4-ARYL-5-(TRIFLUOROMETHYL)OXAZOLES FROM ALDEHYDE iV-METHYE-A-fert-BUTYLHYDRAZONES ... [Pg.72]

Further refinements from these workers led to a general synthesis of 5-aryl(heteroaryl)oxazoles 411 from aromatic and heterocyclic aldehydes using TosMIC and a resin-bound quaternary ammonium hydroxide. This approach greatly simplifies purification. The base and toluenesulfinic acid are removed by simple filtration to afford 411 in quite acceptable purity for biological screening. [Pg.89]

These include the SSA-catalyzed synthesis of heterocyclic compounds such as xanthenes, coumarins, oxazoles, and so on. Xanthenes are of great therapeutic and biological interest on account of their many biological activities such as anti-inflanunatory, antiviral, antibacterial properties, and so on. Seyyed Hamzeh et al. (2008) carried out the SSA-catalyzed synthesis of aryl-14 f-dibenzo[fl,y]xanthenes from aldehydes and P-naphthol and 1,8-dioxo-octahydro-xanthenes from aldehydes and 1,3-dicarbonyl componnd such as dimedone under solvent-free conditions (Schemes 5.25, 5.26). Reactions were carried out at 80°C. Nazeruddin et al. (2011) documented an effective method for 9,10-dihydro-12-aryl-8 f-benzo[a]xanthenes-ll(12 f)-one derivatives in excellent yield and short reaction time using SSA under solvent-free conditions (Scheme 5.27). [Pg.144]

A number of alkylation products from MeOTf and heterocycles have been advocated as useful intermediates. Thus treatment of 2-substituted thiazoles with MeOTf in acetonitrile, followed by reduction of the salt formed with sodium borohydride/CuO in CH2CI2, leads to aldehydes. l-(Benzenesulfonyl)-3-methylimidazolium and l-(/>-toluenesulfonyl)-3-inethylimidaz-olium triflates have been proposed as efficient reagents for the preparation of aryl sulfonamides and aryl sulfonates. MeOTf alkylates 2,5-oxazoles to give salts which can be reduced by PhSiHs/CsP to give 4-oxazolines, and these provide a route to stabilized azomethine ylides. ... [Pg.400]

Many 5-aryl-l,3-oxazoles, bearing various functions at the aryl group, can be prepared in good yields of 68-90% and with high purities from aldehydes and ROMPgel TosMIC reagent 1612 they are purified only by filtration without any need for chromatography [1203]. This makes the method particularly well-suited for use in combinatorial chemistry. [Pg.413]

In a number of multicomponent condensation reactions, TMSCl has also been utilized to inprove the yield or efficacy of the desired product, or is directly incorporated into the final molecules. Examples include the s)fnthesis of Al-aryl-3-arylamino acids from a three-component reaction of phenols, glyoxylates, and anilines, preparation of 2,4,5-trisuhstituted oxazoles, or 4-cyanooxazoles, and the three-component Biginelli reaction (eq 92) and Biginelli-like Mannich reaction of carhamates, aldehydes, and ketones. [Pg.180]


See other pages where Aldehydes 5- aryl oxazoles is mentioned: [Pg.110]    [Pg.253]    [Pg.159]    [Pg.251]    [Pg.142]    [Pg.81]    [Pg.69]    [Pg.136]    [Pg.188]    [Pg.219]    [Pg.195]    [Pg.275]    [Pg.373]    [Pg.156]    [Pg.647]    [Pg.159]    [Pg.18]    [Pg.279]    [Pg.188]    [Pg.219]    [Pg.507]    [Pg.106]    [Pg.87]    [Pg.239]    [Pg.578]    [Pg.114]    [Pg.587]    [Pg.114]   
See also in sourсe #XX -- [ Pg.90 ]




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2-aryl-5- oxazoles

Aldehydes arylation

Aldehydes oxazole

Aryl aldehydes

Arylation oxazoles

Arylations oxazole

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