Proton sponges applications

Rodriguez, I., Sastre, G., Corma, A., Iborra, S. Catalytic Activity of Proton Sponge Application to Knoevenagel Condensation Reactions. J. Catai. 1999, 183, 14-23. 

The main area of application of proton sponges, primarily compound 1, is in organic synthesis as strong but low-nucleophilicity bases. Besides, the proton sponges and their salts are a favourite model of physical chemists and theoreticians for investigating hydrogen bonds and a number of other interesting phenomena. 

Until recently, there had been no reports on the application of 2,7-disubstituted proton sponges like 44 and 65 in organic synthesis. Their advantage in comparison with compound 1 is their increased basicity coupled with their extremely low C-nucleophilicity. Lately, the 2,7-dimethoxy compound 44 was used for deprotonation of salts of other proton sponges, in particular of 88 and 89 (Section n.C.2)67. In another example, when the proton sponge 1 participated in the azo-coupling reaction, the addition of base 44 increased the degree of interaction (equation 30)56. The yield of the azo compound 269 was nearly quantitative, and the base 44 could be easily recovered. 

A kind of technical application of IV-alkylated 1,5- and 1,8-diaminonaphthalenes was also reported. In particular, tetraallyl proton sponge 270, prepared in accord with equation 31, has demonstrated significant antioxidant activity in lubricant compositions. Though the yield of 270 was not mentioned, it was emphasized that its antioxidant properties and its lesser-alkylated precursors work at a concentration of only 0.5%249. 

Some applications of Proton Sponge (1) for pericyclic reactions have been reported. Intramolecular Diels-Alder (IMDA) reaction of triene proceeded under thermal conditions to give bicyclic compound. In this reaction, the yield of the IMDA reaction for the Lewis acid labile substrate was significantly improved to 57% in the presence of a catalytic amount of Proton Sponge (1) (0.3 equiv.) [28] (Scheme 8.9). A similar effect was observed in the IMDA reaction of ester derivative. Whitney et al. conducted the IMDA reaction of acrylate... 

In this chapter, the synthetic utility of Proton Sponge (1) was reviewed. This superbase, although not a main player, is indispensable for various mild and selective transformations in organic synthesis. Despite the unique characteristics of superbases, their exploitation is still limited. Recently, various types of proton sponges, including chiral ones, have been developed, and are likely to have a wide range of applications in organic and asymmetric synthesis. 

Introduction. The principal synthetic application of 3,4-dihydro-2//-pyrido[ 1,2-a]pyrimidin-2-one (1) is an acid scavenger it is an example of a proton sponge (see 1,8-Bis(dimethylamino)naphthalene). The reagent has been used in... 

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