The Ritter Reaction of Terpenes. Part 3. Investigation of Carvone Related Compounds

The Ritter reaction of (R)-carvone (1), cis-carveol (2) and carvyl ethers 3 and 4 was investigated.For ketone 1 formation of 8-amido-6-p-menthen-2-ones (7-12) in moderate yields was observed. Alcohol 2 gave, depending on the reaction conditions, 2-amido- 6,8(9)-p-menthadienes, 2-amido-4(8),6-p-menthadienes and/or 2,8-diamido-6-p-menthenes. Ethers 3 and 4 underwent cleavage to almost the same amides as it was observed for cis-carveol (2). Additionally, tertiary phenylcarveol (5) under similar conditions furnished 6-acetamido-2-phenyl-1,8(9)-p-menthadiene (28) as a result of dehydration, followed by migration of a double bond. The proposed mechanisms of the reactions are presented.