Synthese neuer Nonafulvene

Abstract

Nonafulvenes lc and 1m-S are prepared by the following methods: a) Elimination of AcOH from acetoxyalkyl-cyclononatetraenes (Scheme 2; lm); b) alkylation of nonafulvenolates (Scheme 3, lc, In); c) elimination of alcohol from di-and trialkoxymethyl-cyclononatetraenes (Scheme 5; lo, lp, lq); d) deprotonation of intermediary formed formamidiniumcyclononatetraenes (Scheme 6 ; tr, Is). Scope and limitations of these preparative sequences are discussed and compared with the corresponding pentafulvene syntheses. ') 2, Ted der Dissertation [4]. ' )Ted der Dissertation (51. 4,Postdoctoral fellow 1977/78. 5,Im folgenden wird all-cis -Cyclononatetraenid als CNT-, all-cis-Cyclononatetraen als CNT und cis,clr,cis,trons-Cyclononatetraenid als ccct -CNT-abgekurzt. ' ) Das Nonafulvenolat (bzw. Nonafulventhiolat) 4 befindet sich mit dem entsprechenden Acyl-CNT-(bzw. Thioacyl-CNT-) im Gleichgewicht, dessen Lage durch Substituenten, Solvens, Temperatur und Gegenion beeinflusst wird 1121. 44. Mitt. uber Fulvene, Fulvalene, 43.Mitt. [I]; Kurzmitteilungen 121 131.

Synthetic Attempts towards ‘Aromatic’ Nonafulvenes

“…However, in view of a smooth E2 elimination of HX, the proton as well as the leaving group X should assume a trans-diaxial-arrangement with a dihedral angle close to 180". In the course of our present as well as of earlier experiments [12], we were often surprised to see that, in some cases, E2-type eliminations were proceeding quite easily at low temperature while they did not work in other cases under similar conditions.…”

“…Some of these problems have already been discussed [12] [25]. They are substantially increased by the thermal instability of cyclononatetraenes 8 as well as of most nonafulvenes 1 which in many cases affords reactions -as well as workup procedures -at temperatures below 0".…”

“…For example, HBr elimination from 81 to give 11 proceeds easily at -70°, and even AcOH elimination from 80 to give 10-phenylnonafulvene (lo) is possible at -30" [12], while several attempts to realize HBr elimination from 8k failed to give nonafulvene 4a under various conditions (Scheme 9)"). Of course, the substituent of 8k is relatively bulky (although the fluorene n system is planar).…”

“…Ten years ago, Otnr [13] had reacted Na-(ZZZE)-6 with 7 to give 8g [12] [13], 'H-NMR of which showed signals of vinylic H-atoms between 6.2 and 5.6, H-C(9) at 5.34, NCH, at 4.19 and NCH, at 3.22 ppm. This time [9], the same reaction under similar conditions [9] undoubtedly gave 8e according to the 'H-NMR (300 MHz, CDCI,), with vinylic H-atoms between 6.2 and 5.2, H-C(9) at 4.68, NCH, at 2.61 and CH3 at 2.01 ppm.…”

Synthese und NMR‐Spektren von Nonafulven sowie Vergleich mit 10‐Phenylnonafulven

“…Nach Tieftemperatur-Chromatographie und Tieftemperatur-Kristallisation (-78") wird 6a als farblose Kristalle isoliert. Wie fruher beschrieben [14], fiihrt die analoge Umsetzung von 5b mit K(t-BuO)/THF bei -20" rnit 24% Ausbeute zu blassgelben Kristallen von 10-Phenylnonafulven (6b). Wegen der einleitend erwahnten praparativen Schwierigkeiten blieb das Verfidhren bisher auf die Synthese von 6a und 6b beschrankt.…”