Traceless linkers silyl-based

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-... 

The work by Armstrong was extended to include the room temperature resin capture of trisubstituted ethenes with a pendant boronate group.80 Modification of the amide linker above to a novel silyl-based one allowed for the traceless cleavage of superior analogues. 

The most common anchors for traceless linkage of arenes are based on silyl linkers due to the well-known protodesilylation of the Si-aryl bond. The first traceless silyl linkers were described independently by Ellman et al. and Veber et al. in 1995 [104, 106], Starting from resin-bound arylstannane 113, Ellman has shown the advantages of this type of detachment in the synthesis of a diverse benzodiazepine library (Scheme 16.27). Improvements in the chemoselectivity of the cleav-... 

The traceless anchors based on silicon just described are limited by the need to synthesize a preformed handle consisting of the first building block and the silicon linker. Moreover, traceless release from conventional aryldialkylsilanes is complicated by their low hydrolytic stability and loss of silicon from the resin in the cleavage process. The silyl chloride resin 8h can be used to anchor aryl rings by reaction with aryllithium reagents. The anchor is stable to concentrated TFA and bases, but treatment with TBAF cleaves the final products [353]. 

Newly developed silicon hnkers such as 79 (Scheme 37) have been synthesized in fewer steps as compared with the earlier reported traceless linkers based on silyl functionalization. They allow for an easy binding to the support before performing the combinatorial synthesis [93, 94],... 

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