2-halogen-substituted pyridinium-N-phenacylides and their cycloiminium and acyclic analogs: 1. Synthesis of the parent salts, their betaine-ylides, and oxazolium analogs

A metal-free approach for the synthesis of amides/esters with pyridinium salts of phenacyl bromides via oxidative C–C bond cleavage

“…It is assumed that initially the nucleophilic nitrogen/oxygen attacks the carbonyl carbon of the pyridinium salt of the phenacyl bromide to generate intermediate A . The attack of the ortho -position of the pyridinium moiety by the nucleophilic oxygen of intermediate A is then proposed to generate cyclic oxazolopyridine intermediate B [42–43]. The intermediate B then undergoes a rearrangement to afford N -alkylated benzamide 3 via a C–C bond cleavage with the subsequent release of pyridin-1-ium-1-ylmethanide, which further reacts with hydrogen bromide to form the 1-methylpyridin-1-ium bromide salt.…”