A short-cut from 1-acetyl adamantane to 2-(1-adamantyl)pyrroles

The oxime of 1-acetyl adamantane 2 is added to acetylene (KOH/DMSO, 70 °C, initial acetylene pressure 13 atm, 30 min) to afford the corresponding O-vinyl oxime 5 in 80% yield. The latter upon heating (DMSO, 120 °C, 1 h) gives 2-(1-adamantyl)pyrrole 3, 1-acetyl adamantane 1, and adamantane (6:3:1 mass ratio), the yield of the pyrrole 3 being 83% (based on 1-acetyl adamantane 1 consumed). Under harsher conditions (NaOH/DMSO, 130 °C, atmospheric pressure of acetylene, 4 h) oxime 2 reacts with acetylene to furnish pyrrole 3, 1-acetyl adamantane 1, 1-vinyl adamantane 9, and adamantane (6:7:3:1 mass ratio), with the isolated yield of pyrrole 3 reaching 34%. Under pressure (NaOH/DMSO, 120 °C, initial acetylene pressure 14 atm, 1 h) the same reaction leads to 2-(1-adamantyl)-1-vinylpyrrole 4 and ketone 1 in 48% (based on consumed ketone 1) and 24% yields, respectively. The pyrrole 4 is easily deprotected to the corresponding 1H-pyrrole 3 in 77% yield by treatment (aqueous MeCN) with Hg(OAc)2 and NaBH4.