Study On The Tandem Mannich Reaction And O-alkylation Of Oximes

In this paper, we carefully studied the Mannich reaction between ketones and aromatic imines induced by radical cation and iodine. O-Alkylation of oximes was also achieved under radical cation induced conditions. A series of important compounds were synthesized, giving the following results:1. Tris(4-bromophenyl)aminium hexachloroantimonate (TBPA^+.) can induce the Mannich reaction of aromatic imines and ketones, producing a series ofβ-amino ketones and 4-piperidone derivatives in high selectivity way. We proposed a single electron transfer mechanism supported by several evidences.2. Based on the results obtained, we further optimized the reaction conditions in order to perform the synthesis of 4-piperidones. We found iodine as Lewis acid could efficiently catalyzed this tandem Mannich reaction producing 4-piperidones in high yields together with high selectivity which promoted the applications of this reaction towards the synthesis of heterocyclic compounds containing nitrogen.3. O-Alkylation initiated by radical cation salts was achieved through the reaction between N-vinylamides and oximes under base free conditions, synthesized a series of oxime ethers in high yields. We also studied the mechanism carefully and found that under radical cation induced conditions only O-alkylation reaction occurred and no N-alkylation products were isolated.