Solid supports hydrochloride

Recently, Kerr introduced a promoter anchored to a solid support to facilitate workup after the reaction. For example, the PKR proceeds to completion by use of the amine A-oxide anchored on solid support 14, and then the polymeric amine is recovered by simple filtration. The recovered polymer is cleaned by washing with a THF-aqueous 2 M HGl mixture (2 1 mixture), followed by washing of hydrochloride salt with a 10% solution of Pr2NEt in DMF. The resultant resin is oxidized again and then used without loss of activities.Kerr and Pauson also successfully employed sulfide promoters anchored on the solid support 15 for this cycloaddition (Figure 1). ... 

As higher reactivity of electron-rich triazenes was observed, p-alkoxy-substituted anilines were selected as an efficient starting material. Solid-supported triazenes were prepared via a solid-phase bound nitroaryl, which was reduced to the polymeric ammonium hydrochloride resin 8 (Fig. 7). 

The S-layer lattices can be disrupted by chemical agents such as guanidinium hydrochloride (GuHCl). Upon removal of the chemical, the monomers reassemble in vitro in solution or on a solid support, for example, silicon wafers (Pum and Sleytr, 1995). 

The final conditions were scaled up with no problems chalcone 8a and guanidine (liberated from its hydrochloride with sodium ethoxide) were heated in dimethyl acetamide while bubbling air through the mixture to form pyrimidine 9a. After complete conversion (16 h), the product was cleaved from the support (20% trifluoroacetic acid in DCM). Pure 4-(2-amino-6-phenyl-pyrimidin-4-yl)bcnzamidc 1 was obtained as its trifluoroacetate salt upon evaporation of the filtrate and recrystallisation of the residue from ethanol/water in 56% overall yield based on the solid phase attached 4-carboxybenzaldehyde 6a. 

In a preferred example, when UDMH in anhydrous THF was added to a solution of 1-chloroethyl chloroformate in THF at 10-20°C, the intermediate carbazate (a) was formed. After filtration to remove the UDMH hydrochloride, we accomplished a cyclisation to (b) just by refluxing the THF solution for 1 h.. The resulting hygroscopic salt (b) precipited immediately in 71 % overall yield. In solid form, (b) is stable undefinitely at room temperature. The cyclic aminimide (c) was then easily prepared from (b) by treatment with a resin supported base in high yield. The three steps of the synthesis are depicted in scheme 145. 

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