Enantioselektive Terpensynthesen durch Diels-Alder-Reaktion von 1-(1-Arylalkoxy)-2-methyl-1,3-butadien mit Isopren

✍ Scribed by Zadel, Guido ;Rieger, Rainer ;Breitmaier, Eberhard

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 355 KB
• Volume: 1991
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.1991199101229

✦ Synopsis

Enantioselective Terpene Syntheses by Diels‐Alder Reaction of 1‐(1‐Arylalkoxy)‐2‐methyl‐1,3‐butadiene with Isoprene

The (R)‐ and (S)‐1‐(1‐arylalkoxy)‐2‐methyl‐1,3‐butadienes 6 undergo [4 + 2] cycloadditions with excess isoprene (7) under pressure to yield not only the expected (4__S__,6__R__)‐ and (4__R__,6__S__)‐trans‐carveol (8) with up to 96% e.e. but also up to 40% of (R)‐ and (S)‐limonene (9) with up to 93% e.e. Asymmetric induction is proposed to arise from a transition state involving definite π stacking of one molecule of isoprenyl ether and two molecules of isoprene.