Direkte und indirekte metallierung von endo-dicylopentadien. 119Sn- und 13C-NMR studie stannylierter folgeprodukte
- Additional Document Info
- View All
endo-Dicyclopentadiene (1) can be metalated by use of simple procedures with good overall yields. The attack occurs at the various vinyl, rather than at the allyl, positions of 1 as was confirmed by trapping the carbanions with Me3SnCl. When t-BuLi/TMEDA are used, the 8- and 9-stannyl derivatives (3 and 4) are formed, whereas an excess of n-BuLi/t-BuOK leads to doubly stannylated derivatives with Me3Sn groups in position 4 8 (6), 4 9 (7), and 3 9 (8) in addition to 3 and 4. Furthermore the latter reaction yields 5,5-bis(trimethylstannyl)cyclopentadiene (5). With stoichiometric amounts of n-BuLi/t-BuOK the formation of 3 and 4 predominates over that of 5-8. 5 is obtained from 1 after deprotonation at the allyl position, followed by an extremely fast retro-Diels-Alder reaction and then by further deprotonation. This follows from two experiments: (1) exo- and endo-5-trimethylstannyl-endo-dicyclopentadiene (11 and 12) which are synthesized from 1 in three steps give cyclopentadienyllithium and 1 when treated with methyllithium at -78°C; (2) cyclopentadiene reacts with an excess of n-BuLi/t-BuOK and Me3SnCl to give 5. When 12 is heated syn-10-trimethylstannyl-endo-dicyclopentadiene (13) is obtained. The eight stannyl derivatives of 1 are identified mainly from the following NMR parameters: δ(119Sn), δ(13C), δ(1H), nJ(119/117Sn13C), and 6J(119Sn119/117Sn). The 13C NMR satellite spectrum of 1 yields the isotope shifts 1Δ13(i(13C(j)) and 1J(13C13C). The latter lead to the revision of earlier signal assignments. © 1988.
author list (cited authors)
Blümel, J., & Köhler, F. H.