Traceless germanium-based linkers

Chemistry similar to this was used in Ellman s paper to promote application of a silicon-based traceless linker.62 The full report on this work63 shows that both aliphatic and aromatic acid chlorides may be used in the coupling step. The same,approach is also shown to be successful with a germanium-based linker in place of the silicon. The couplings were typically performed for 1 h only, with equilibration time of a few minutes... 

Sdieme 101 Germanium-based linkers for traceless release and formation of haloarenes... 

Cleavage of all the linkers described above provide a functional group (carboxylic acid, amide, amine, etc) at the anchoring position. Silyl-based handles 71,72, and 73 as well as germanium-based handle 74 insert a C-H bond at the anchoring position and are referred to as traceless (Fig. 15) [82-... 

For the attachment and the traceless release of electron-deficient aromatics, germanium-based hnkers of type 89 (Fig. 10) have been developed [103, 104]. This linker has the advantage that it is fairly stable towards strongly basic conditions and strong nucleophiles. 

Generation of a-ketoenamines (Table 8, entry 8) [456] Spivey et al. [456] performed a pyrazole synthesis with a polymer-supported acetophenone and a germanium-based traceless linker. The support-bound acetophenone was allowed to react with dimethylformamide dimethyl acetal (Bredereck s reagent) [498]. Subsequent reaction of the resulting a-ketoenamine with aryl hydrazine hydrochlorides gave the pyrazoles. 

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