Benzylaminomethyl polystyrene

The von Richter cinnoline process was further extended to solid-phase synthesis. The route began from benzylaminomethyl polystyrene and the required diverse o-haloaryl resins represented by 21 were prepared from substituted o-haloanilines. A Pd-mediated cross-coupling reaction with 21 and the alkynes provided the alkynylaryl derivatives represented by alkyne 22. The von Richter cyclization reaction with hydrobromic or hydrochloric acid in acetone/HaO and cleavage from the resin occurred in the same step to furnish the cinnoline derivatives 23 in 47-95% yield and 60-90% purity (no yield reported for each entry). 

Starting from commercially available 2-fluoro-5-nitroaniline, this aniline was diazotized and coupled to benzylaminomethyl polystyrene to give the immobilized triazene 36 (see Experimental section). At this point, it was crucial to avoid using hydroxylic solvents such as methanol in the washing steps since these solvents are known to react with fluorotriazenes. Acetone was found to be a good substitute for methanol. 

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