Ugi reactions fluorous

Benzimidazoles 248 - fluorous Ugi reactions 115 Benzo[fc]furans 247 Benzo[i)]thiophenes 248 Benzocondensed heterocycles 246,249, 252... 

Farnesyl protein inhibitor 2 Flavones 254 Fluorous phases 112 Fluorous Ugi reactions 115 Functional group transformations 25... 

New fluorous reactions also present entertaining naming opportunities. For example, we call the fluorous Ugi reaction the flugi reaction. The fluginelli reactions follows accordingly. 

Microwave-assisted fluorous Ugi reactions were presented where the reaction times and convenient separation techniques appeared more attractive than the corresponding room temperature methods with traditional scavenging techniques. ... 

Zhang W, Tempest P (2004) Highly efficient microwave-assisted fluorous Ugi and post-condensation reactions for benzimidazoles and quinoxalinones. Tetrahedron Lett 45 6757-6760... 

The Ugi reaction involves components of aldehyde, acid, amine, and isocyanide. Scheme 13 shows an Ugi reaction using fluorous benzyl-attached... 

The efficiency of an Ugi/de-Boc/cycUzation strategy for constmction of heterocy-chc compounds has been improved through the incorporation of MW and fluorous technologies. In the synthesis of substimted quinoxalinones and benzimidazoles, a flnorous-Boc-protected diamine is employed for the Ugi reactions. Both the Ugi and the post-condensation reaction proceed rapidly under MW irradiation and the reaction mixtures are purified by solid-phase extraction (SPE) over fluoro flash cartridges (Scheme 3.42) [102]. 

In the synthesis of substituted quinoxalinones and benzimidazoles, a fluorous-Boc protected diamine has been used for the Ugi reactions. 

Furthermore, multicomponent reactions can also be performed under fluorous-phase conditions, as shown for the Ugi four-component reaction [96], To improve the efficiency of a recently reported Ugi/de-Boc/cyclization strategy, Zhang and Tempest introduced a fluorous Boc group for amine protection and carried out the Ugi multicomponent condensation under microwave irradiation (Scheme 7.84). The desired fluorous condensation products were easily separated by fluorous solid-phase extraction (F-SPE) and deprotected by treatment with trifluoroacetic acid/tet-rahydrofuran under microwave irradiation. The resulting quinoxalinones were purified by a second F-SPE to furnish the products in excellent purity. This methodology was also applied in a benzimidazole synthesis, employing benzoic acid as a substrate. 

In a fluorous variant of the Ugi and Biginelli multicomponent reactions, it has been... 

The time consuming chromatographical purification of heterocycles 28 and 29 slowed down the rate of library production. A phase separation using fluorous chemistry was employed by Zhang and Lu to address the workup and purification of fused 3-aminoimidazo[ l,2-a]pyridines (such as 30) [54]. Thus, attachment of a perfluorooctanesulfonyl tag to aldehydes and subsequent Ugi three-component microwave-assisted condensations with 2-aminopyridines and isocyanides furnished the desired heterocycles 30, which were conveniently isolated by fluorous solid-phase extraction. The fluorous tag could be subsequently used as an activating group in the post-condensation modifications, such as Suzuki-Miyaura cross-coupling reactions. 

Scheme 3.17 Fiuorous variants of the Ugi (above) and Bigineiii muiti-component reactions (beloiv) enabie the purification of the primary fluorous condensation products (not shown in this scheme) by simple two- or three-phase extraction, followed by "traceless" cleavage of the fluorous silyl tag with TBAF [5].

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