Ortho amides amidine synthesis

Since the discovery of the synthesis of 1,3,5-triazine-2,4-diamines from biguanide and its derivatives,328-329 a large variety of carboxylic acid derivatives, e.g. acid chlorides,332 342,346 lactones,333 amides,334,335 imides,336,337 ortho esters,338 amidines,338 esters334, 339- 343 and acid anhydrides,332,344,345 have been used as starting materials in the preparation of these triazines (Table 8).330,331 The preferred procedure is the reaction of biguanides 1 with esters 2 in alcoholic solution, sometimes in the presence of a basic catalyst. The reaction mechanism is thought to be as indicated.341... 

The presence of the ortho-riiXro group allowed nucleophilic cleavage to liberate the desired amine [6]. An amidine linker [7,8] provided a resin bound amine that was stable to oxidative, reductive, and alkylative conditions. The use of 2-chlorotrityl resin proved to be useful for the preparation of a secondary amine library [9] as well as hydroxamic acids [10]. Tertiary amines were prepared by 1,4 addition to a resin bound acrylate followed quatemization and a retro-Michael reaction [11]. The p-nitrophenyl carbonate linker has been shown to be useful for the inunobilization of ben-zamidines [12] and for the synthesis of sulfonamides [13]. Sulfonamides and amides were also prepared using a halogenated Wang resin [14]. 

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