Imidazolium carboxylates

An analogous reaction was carried out with ter/-butyl alcohol to give the imidazolium carboxylate in 77% yield and the azido formic ester in 85% yield.[l37]... 

Analogously to these reactions of imidazolium carboxylates, the introduction of urethane-type amino-protecting groups can be accomplished with the following mesoionic azolides [194]... 

Reaction of imidazolide with carboxylic acid in a 1 2 ratio at room temperature leads to carboxylic acid antydride and imidazolium carboxylate. 

Scheme 5.4 Formation of 2-dialkyl-imidazolium-carboxylates following the Kolbe-Schmitt synthetic procedure [27].

Scheme 5.8 Formation of sodium carboxylates with 2-dialkyl-imidazolium-carboxylate as the C02-carrier [40].

Figure 4 Histograms of N O hydrogen bonding distances. A systematic dependence of N O distance on ApXa appears in these data. Both X-ray and neutron diffraction data are from the CSD. From top to bottom all N—H O imidazolium-carboxylate, ApXa 3 ammonium-cargoxylate, ApXa 5 amide-amide, ApXa 15 amide-water, ApXa 17. The pXa values used here are based on typical aqueous values.

RHODIUM AND IRIDIUM A-HETEROCYCLIC CARBENE COMPLEXES FROM IMIDAZOLIUM CARBOXYLATES... 

Charge-assisted (-l-)N-H...O(-) hydrogen bonds also promote the formation of ID chains comprising imidazolium and arenecarboxylate ions (Fig. 3f). If dicarboxylic acids are used, the ID chains can be stitched into 2D sheets by Speakman-type -COO . .. HOOC- hydrogen bonds [28]. The imidazolium-carboxylate hydrogen bond has also been used to construct a series of isostrucmral layered materials containing different transition metal ions [29]. 

The enthalpy of vaporization, estimated according to Zaitsau et al. [175] as shown above yielded the ce = Ay// - RT and the ced, which were then used for other purposes by Singh and Kumar [185]. This approach was also used by Xu et al. [202] to obtain the Ay// and values of four imidazolium carboxylate RTlLs... 

A novel synthetic route to NHC complex species involving C-C aetivation of imidazolium carboxylates was also characterized computationally, with the reaction being driven by the release of a CO2 molecule. 

N-oxides, KHSO5 and oxaziridines. Molecular oxygen can also be used in the presence of an electron source. The use of hydrogen peroxide often results in oxidative decomposition of the catalyst due to the potency of this oxidant. However, the introduction of chlorinated porphyrins (1) (Scheme 2.7) allowed for hydrogen peroxide to be used as the terminal oxidant [27]. These catalysts, discovered by Mansuy and coworkers, were demonstrated to resist decomposition, and when used together with imidazole or imidazolium carboxylates as additives, efficient epoxidation of alkenes were achieved (Table 2.3, entries 1 and 2). 

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