Triazenes as robust and simple linkers for amines in solid-phase organic synthesis

The Structural Influence in the Stability of Polymer‐Bound Diazonium Salts

“…This means that, in this evaluation, the diazonium ion p-Cl-C 6 H 4 N 2 BF 4 is the most stable both in the free form and in the complexed state. According to the results in Table 1, p-Cl-C 6 H 4 N 2 BF 4 in the uncomplexed form is approximately 3500 times more stable than m-CH 3 O-C 6 H 4 N 2 BF 4 , which indicates that the T2 linker [24,25] is the most unstable diazonium salt. Furthermore, p-Cl-C 6 H 4 N 2 BF 4 is stabilized with [18]crown-6 by a factor of 10 and with [21]crown-7 by a factor of 60.…”

“…[1,17] The ORTEP structure of this benzenediazonium hexafluorophosphate complex with [18]crown-6 is accessible. [18] The structures of 4-methoxybenzenediazonium tetrafluoroborate with [21]crown-7 [19] ( Figure 2) or dibenzo [24]crown-8, respectively, have also been published. [20] All these structures show that the crown ether complexes the diazenyl group.…”

Polymer‐Supported Triazenes as Smart Reagents for the Alkylation of Carboxylic Acids

“…Other reducing agents (Na 2 S 2 O 4 /H 2 O [14] at 70 8C, Na 2 S/S/H 2 O [15] at 150 8C and 6 bar or SnCl 2 ¥ 2 H 2 O/EtOH [16] at 70 8C) were ineffective according to elemental analysis. Classical aqueous diazotation [14] with HCl/NaNO 2 led successfully to the polymer-bound diazonium salt 4, whilst diazotation with tertbutylnitrite/BF 3 ¥ Et 2 O [11,17] or NOBF 4 [18] in organic solvents was less successful. The diazotation reaction was best monitored by quenching samples of 4 with amine and checking the activity of the resulting PST 5.…”

“…[9] Furthermore, PSTs have been used as cleavable supports for solid-phase synthesis. [10,11] We describe here further examples of the synthetic scope of PSTs as alkylating agents, and in particular we describe an improved procedure for their preparation. It involves an efficient four-step synthesis starting from simple polystyrene rather than from the more expensive chloromethyl polystyrene used by Rademann and Br‰se.…”

Diversity Linker Units for Solid‐Phase Organic Synthesis

“…T2 linkers are resin-bound diazonium salts used for the immobilization of amines and other nitrogenous compounds. [36,37] Diversity cleavage has been demonstrated by using a range of "traditional" reactions to derivatise target molecules (Scheme 12). For example, reaction Scheme 13. with carboxylic acids has been shown to give the simple esters 30, [38] whereas cleavage with sulfonic acids provides the sulfonate esters 31 [39] and cleavage with trimethylsilyl halides or simple acids gives the corresponding alkyl halides, acetates and trifluoroacetates 32.…”