Sommelet-Hauser or Stevens Rearrangement of 1-Methyl-2-(substituted phenyl)piperazinium 1-Methylides. Ring Enlargement of Piperazines to Seven- or Nine-Membered Cyclic Amines.

Fluoride ion-induced desilylation of 4-acetyl-1-methyl-2-(4-substituted phenyl)-1-trimethylsilyl-methylpiperazinium iodides 5 gave 5-acetyl-2-methyl-10-substituted 1,3,4,5,6,11a-hexahydro-2H-2,5-benzodiazonines 7 and/or 5-acetyl-2-methyl-10-substituted 2,3,4,5,6,7-hexahydro-1H-2,5-benzodiazonines 8(Sommelet–Hauser rearrangement products). However, a similar treatment of 1-methyl-3-oxo-2-phenyl-1-trimethylsilylmethylpiperazinium iodide 10 afforded 1-methyl-6-phenyl-2,3,6,7-tetrahydro-1H-diazepine-5-one 12(Stevens rearrangement product).