The Twofold Heck Reaction on 1,2-Dihalocycloalkenes and Subsequent 6π-Electrocyclization of the Resulting (E, Z, E)-1,3,5-Hexatrienes: A New Formal {2+2+2}-Assembly of Six-Membered Rings
✍ Scribed by Katharina Voigt; Paultheo von Zezschwitz; Keith Rosauer; Annegret Lansky; Amy Adams; Oliver Reiser; Armin de Meijere
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 490 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-193X
No coin nor oath required. For personal study only.
✦ Synopsis
1,6-Disubstituted (E,Z,E)-1,3,5-hexatrienes (4 and 5) were hex-1-ene (19) or by Wittig-Horner-Emmons olefination of 2bromocyclohexene-1-carbaldehyde ( 24) and subsequent prepared by vicinal twofold Heck coupling reactions from 1,2-dibromocyclopentene (1), 1,2-dibromocyclohexene (2), Heck reaction of the resulting (E,Z)-bromodienes 25. Several of the hexatrienes (4aa, ee, 5aa, ee, al, am, el) readily 1,2-diiodocyclopentene ( 8), 1,2-diiodocyclohexene ( 9), 1bromo-2-trifluoromethanesulfonyloxycyclohex-1-ene ( 11), or underwent a 6π-electrocyclization upon heating in an inert atmosphere to give the 5-or 6-ring-annelated cis-5,6-1-chloro-2-nonafluorobutanesulfonyloxycyclohex-1-ene ( 19) with alkenes 3, e. g. methyl, tert-butyl, menthyl, 8-disubstituted cyclohexadienes 26, 27 (50-95 %). Starting from 5am 2,3-disubstituted tetrahydronaphthalene 28am was phenylmenthyl acrylate, styrene, and alkenylsilanes, respectively, in moderate to mostly good and very good formed under oxidative conditions (air) in the reaction and in the work-up procedure. The bissilyl-substituted derivatives yields (20-92 %). The coupling of alkenylsilanes 3f؊k could only be achieved with the 1,2-diiodocycloalkenes 8 and 9, 4ff, jj, 5ff did not cyclize under thermal conditions, apparently due to the steric demand of the two silyl respectively. The corresponding hexatrienes 5 with two different substituents in the 1-and 6-positions were prepared substituents which would have to end up cis with respect to each other in the cyclohexadiene products. by a sequence of two coupling reactions with different alkenes from 1-chloro-2-nonafluorobutanesulfonyloxycyclo-