Acid-Catalysed Dehydration of Tricyclic Unsaturated Alcohols

✍ Scribed by Kenji Hayakawa; Hans Schmid

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: German
• Weight: 975 KB
• Volume: 60
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19770600512

✦ Synopsis

The tricyclic alcohols 3-7, derived from the corresponding ketones 1 and 2 (Scheme I ) , by action of acids underwent dehydration with skeletal rearrangements. Dehydration of 3 and 4 with POCI3/pyridine (procedure A) afforded the polycyclic hydrocarbons 9,10, and 12,13, respectively. With TsOH (procedure B), on the other hand, 3 and 4 gave homo-triquinacenes 10 and 14 respectively, as well as the polycyclic ethers 11 or 15 (Scheme 2). Hydrocarbon 9 (or 12) was converted into 10 (or 14) by treatment with TsOH (Scheme 3). Ketone 1 isomerized similarly with FS03H to the tertiary alcohol 16 (Scheme 4). Plausible mechanisms for these transformations are summarized in Scheme 8. Dehydration of the secondary alcohols 5 and 7 was effected only by procedure A. While treatment of alcohol 5 with POCl,/pyridine yielded two isomeric hydrocarbons 17 and 18, similar dehydration of its epimeric alcohol 7 afforded hydrocarbon 21 as the sole product. The tertiary alcohol 6 was dehydrated by both procedures to yield two isomeric hydrocarbons 19 and 20 (Scheme 5). Hydrocarbon 20 was converted into 19 by procedure B (mechanisms, Scheme lo). Reaction of ketone 2 with CF,COOH gave the addition product 22 converted into vinylsulfonyl fluorides 24 and 25 by treatment with FS0,H (Scheme 6). Homo-triquinacenes 10 and 14 reacted smoothly with 4-phenyl-1,2,4-triazoline-3,5-dione to give the 'ene'-reaction products 26 and 27, respectively.