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Aldehydes multicomponent

A number of microwave-assisted multicomponent methods for the synthesis of imidazoles have been reported [68-71 ]. The irradiation of a 1,2-diketone and aldehyde with ammonium acetate in acetic acid for 5 min at 180 °C in a single-mode reactor provides alkyl-, aryl-, and heteroaryl-substituted imidazoles 39 in excellent yield (Scheme 14) and this method has been used for the rapid and efficient preparation of two biologically active imidazoles, lepidiline B and trifenagrel [68]. [Pg.43]

A library of 800 substituted prolines of type 112 was described using a similar synthetic approach. The [3 + 2] cycloaddition occurred via a multicomponent reaction of a-amino esters, aldehydes, and maleimides (Scheme 38). [Pg.234]

Another kind of combinatorial synthesis can be applied to reactions that assemble the product from several components in a single step, a multicomponent reaction. A particularly interesting four-component reaction is the Ugi reaction, which generates dipeptides from an isocyanide, an aldehyde, an amine, and a carboxylic acid. [Pg.1256]

Recently, a new multicomponent condensation strategy for the stereocontrolled synthesis of polysubstituted tetrahydropyran derivatives was re-published by the Marko group, employing an ene reaction combined with an intramolecular Sakurai cyclization (IMSC) (Scheme 1.14) [14]. The initial step is an Et2AlCl-promoted ene reaction between allylsilane 1-50 and an aldehyde to afford the (Z)-homoallylic alcohol 1-51, with good control of the geometry of the double bond. Subsequent Lewis acid-media ted condensation of 1-51 with another equivalent of an aldehyde provided the polysubstituted exo-methylene tetrahydropyran 1-53 stereoselectively and... [Pg.19]

A classical non-isocyanide-based multicomponent process is the Biginelli dihydropyrimidine synthesis from 3-keto esters, aldehydes and urea or thiourea [63], The transformation was first reported in 1893 [64], but during the early part of the... [Pg.557]

Other multicomponent reactions are exemplified in the following two schemes. A new highly diastereoselective four-component reaction was developed for the synthesis of dihydropyridones 191 substituted with an isocyanide functionality <06OL5369>, thereby generating a synthetically useful complex isocyanide for use in further reactions. In this strategy, a phosphonate, a nitrile, and an aldehyde are used to generate an azadiene intermediate 192, which is trapped by an isocyanoacetate in the same pot. [Pg.341]

Another multicomponent synthesis giving N-3-substituted compounds 28 consisted of the sequential reaction of metallated phosphonoacetates, in one pot, with a nitrile then an aldehyde and finally an isocyanate. This was an extensive study of the scope and limitations of the different substituents on all the components. The most important feature was that, for good yields, the isocyanate should bear an electron-withdrawing group - tosyl was the most successful. However, an exchange reaction could be carried out by reaction of the tosyl products with aryl isocyanates under microwave irradiation, giving the N-3-aryl derivatives 29 <06CEJ7178>. [Pg.391]

Another frequently used multicomponent reaction is the Kindler thioamide synthesis (the condensation of an aldehyde, an amine, and sulfur). The Kappe group has described a microwave-assisted protocol utilizing a diverse selection of 13 aldehyde and 12 amine precursors in the construction of a representative 34-member library of substituted thioamides (Scheme 6.114) [226]. The three-component con-... [Pg.183]

In 2001, Sarko and coworkers disclosed the synthesis of an 800-membered solution-phase library of substituted prolines based on multicomponent chemistry (Scheme 6.187) [349]. The process involved microwave irradiation of an a-amino ester with 1.1 equivalents of an aldehyde in 1,2-dichloroethane or N,N-dimethyl-formamide at 180 °C for 2 min. After cooling, 0.8 equivalents of a maleimide dipo-larophile was added to the solution of the imine, and the mixture was subjected to microwave irradiation at 180 °C for a further 5 min. This produced the desired products in good yields and purities, as determined by HPLC, after scavenging excess aldehyde with polymer-supported sulfonylhydrazide resin. Analysis of each compound by LC-MS verified its purity and identity, thus indicating that a high quality library had been produced. [Pg.227]

A different multicomponent route to imidazoles has been described by the group of O Shea, involving the diversity-tolerant three-component condensation of an aldehyde, a 2-oxo-thioacetamide, and an alkyl bromide (5 equivalents) in the presence of ammonium acetate (Scheme 6.201) [364]. This allowed the preparation of a 24-membered 4(5)-alkylthio-lH-imidazole demonstration library from 21 different aldehydes, 12 alkyl bromides, and two 2-oxo-thioacetamides. The library was synthesized in a parallel format using a custom-built reaction vessel. Alkylthioimidazoles... [Pg.235]

A multicomponent assembly of pyrido-fused tetrahydroquinolines has been accomplished by Lavilla and coworkers in a one-pot process by the interaction of dihydroazines, aldehydes, and anilines (Scheme 6.242) [425], The reactions were conducted with 20 mol% of scandium(III) triflate as a catalyst in dry acetonitrile in the presence of 4 A molecular sieves, employing equimolar amounts of the building blocks. This protocol provided the cycloadducts shown in Scheme 6.242 in 80% yield as a 2 1 mixture of diastereoisomers following microwave irradiation at 80 °C for 5 min. The same reaction at room temperature required 12 h to reach completion. [Pg.258]

Multicomponent reactions (MCR), in which three or more reactions combine to give a single product, have lately received much attention. The Ugi four-component condensation in which an amine, an aldehyde or ketone, a carboxylic acid, and an isocyanide combine to yield an ot-acylamino amide, is particularly interesting, because... [Pg.409]

Multicomponent reaction systems are highly valued in solid-phase organic synthesis because several elements of diversity can be introduced in a single transformation.1 The Mannich reaction is a classic example of a three-component system in which an active hydrogen component, such as a terminal alkyne, undergoes condensation with the putative imine species formed from the condensation of an amine with an aldehyde.2 The resultant Mannich adducts contain at least three potential sites for diversification specifically, each individual component—the amine, aldehyde, and alkyne—can be varied in structure and thus provide an element of diversity. [Pg.50]

Multicomponent Ugi reaction a resin-bound amino acid is reacted with an aldehyde, isocyanide, and a second amino acid in a one-pot reaction to form the Malkylated cyclic precursor dimer. ... [Pg.676]

The four component Ugi reaction is a condensation between a carboxylic acid, a ketone or an aldehyde, an amine and an isonitrile. Basically each of the reaction components can be attached to the resin. The Ugi reaction is employed for the synthesis of small molecule combinatorial libraries on solid supports. Recently a novel resin bound isonitrile has been used in the Ugi multicomponent reaction for synthesizing diversity libraries of diketopiperazines and benzodiazepindiones (Scheme 3.25) [285]. [Pg.172]

One-pot condensation of an aromatic aldehyde, urea, and ethyl acetoacetate in the acidic ethanolic solution and expansion of such a condensation thereof. It belongs to a class of transformations called multicomponent reactions (MCRs). [Pg.51]

Perhaps the most useful and most widely employed multicomponent reaction in this context is the Ugi four-component reaction (U4CR and variations, Fig. 11), where an isonitrile, an aldehyde, an amine, and a carboxylic acid react to form a single product [65, 66]. The principal product is a dipeptide or dipeptide derivative and a high degree of diversity can be introduced by substituents (each of the four components can be varied), subsequent reactions, or by other reaction paths, which can lead to a vast varia-... [Pg.154]

It should be noted that carbonyl compounds, more often aldehydes, are usual second reagent in both the groups. Other building-blocks in these multicomponent processes, leading to the formation of five-, six-, and seven-membered heterocycles, can be numerous acids and their derivatives, p-dicarbonyl compounds or other CH-acids, isocyanides, etc. At this, three-component reactions of ABC and ABB types [32] are the most typical for aminoazole, although some four-component ABCC processes were also published. [Pg.43]

In several subsequent publications, this promising multicomponent synthetic approach was used for the synthesis of certain types of biologically active heterocyclic compounds. For instance. Boros and co-authors [35] reported application of the three-component heterocyclization between bicyclic aminoazole 2, acetoacetic acid derivatives 3, and aldehyde 4 to obtain compound 5 being aza-analog of known [36] agonist of the calcetonine receptor (Scheme 4). [Pg.45]

In some cases a choice of multicomponent or linear protocol for the treatment of pyruvic acids, aminoazole, and aldehydes allows obtaining different heterocycles. For instance, MCR involving 5-aminopyrazoles or sequence pathway via preliminary synthesis of arylidenpyruvic acids led to positional isomers 36 and 37, respectively (Scheme 15) [4, 61, 68]. It is interesting to note that the same strategy applied to 3-amino-l,2,4-triazole or to amino-W-aryl-lH-pyrazole-4-carboxamide reactions gave no effect and the final compound for both the protocols were the same [52, 61, 62]. [Pg.52]

As CH-acids in the MCRs with aldehydes and aminoazoles, other classes of organic compounds were used as well. Cyanoacetic acid derivatives, acetoyl(aroyl) acetonitriles, ketosulfones, acetophenones, and other reagents were successfully introduced into these three-component heterocyclizations. For example, synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles 40 was carried out as the multicomponent treatment of 5-aminopyrazole, aldehyde, and benzoylacetonitriles solvent-free by fusion either in ammonium acetate at 120°C or in boiling ethanol with EtsN (Scheme 17) [69]. The second approach gave the worst results from the viewpoint of yields and purity of the target compounds. [Pg.53]

For example, it was reported in several independent articles that multicomponent treatment of 5-amino-3-methylpyrazles with 1,3-cyclohexandiones and aldehydes under refluxing in EtOH [82, 83], in DMF with methanol [84], or with application of continuous-flow microwave-assisted procedure in DMSO [85] yielded exclusively pyrazoloquinolinones 50 (Scheme 23). On the other hand, the treatment of 3-unsub-stituted 5-aminopyrazoles with cyclic p-diketones or ketosulfones gave mixtures of Hantzsch dihydropyridines 51 and Biginelly dihydropyrimidines 52 in different ratios [86]. [Pg.56]

On the other hand, Lipson and co-authors in their pubhcations described numerous MCRs of cyclic (3-dicarbonyl compounds and aldehydes with 5-amino-3-methylpy-razole [84], 3-amino-1,2,4-triazole [90], 3-amino-5-methyltio-l,2,4-triazole [91], 2-aminobenimidazole [92], and 2,5-diamino-l,2,4-triazole [93]. It was shown that multicomponent treatments studied in the case of these aminoazoles should proceed via preliminary formation of corresponding enamines, which were isolated and subsequently transformed into target heterocycles (Scheme 28). Intermediates... [Pg.59]

Quiroga and co-authors [101] also reported eco-friendly solvent-free approach to the synthesis of fused benzo[fjpyrazolo[3,4-b]quinolines 72 by three-component reaction of 5-aminopyrazoles, aldehydes, and p-tetralone accomplished by fusion procedure (Scheme 32). However, this method was found inapplicable for the similar reaction of a-tetralone - multicomponent procedure allowed obtaining only bispyrazolopyridines 74 instead of benzo[h]pyrazolo[3,4-b]quinolines 73. According to these experimental results, the latter were generated via preliminary synthesis of arylidentetralones 75. [Pg.62]

Significant contribution in the studying of the MCRs based on aminoazoles, aldehydes, and Meldrum s acid was made by Lipson and co-authors in their publications [ 114—119]. It was established that in some cases these multicomponent treatments can yield positional isomers. For example, refluxing of 3-amino-l,2,4-triazole with aldehydes and Meldrum s acid gave only triazolopyrimidinones 82 [114] (Scheme 36). On the other hand, MCRs involving 3-amino-5-methylthio-1,2,4-triazoles in boiling DMF yielded solely 5-pyrimidinones 83, while the... [Pg.65]

Here we discuss several examples of the multicomponent processes involving aminoazoles, aldehydes, and other organic components such as mercaptoacids, haloacetic acids and their ester, a,p-unsaturated imines, etc., which were not incorporated into the previous two sections of the review. [Pg.72]

Along with the formation of dihydropyrimidine derivatives, an unusual directions of multicomponent treatment of 2,4-dioxobutanoates with aldehydes and several aminoazoles were described by Gein and co-authors [151]. Thus, fusion of carbonyl compounds with 3,5-diamino-l,2,4-triazole gave as usual for this type... [Pg.78]

Keimg et al. describes the optimization of 2-imino-piperazines using Lewis acids to catalyze the multicomponent a-amino amidine synthesis to make piperazines 39 (Scheme 6) [26]. A, Af -(jimethylethylenediamine 36 was used with an aldehyde 37 and isocyanide 38 in methanol with scandium (III) trifluoromethane sulfonate (Sc(OTf)3) as a catalyst to obtain the piperazine 39 in 57% yield. [Pg.94]


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Aldehydes multicomponent cascade reactions

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