All-cis-9.9′-Bicyclonona-1.3.5.7-Tetraenyl und dessen dianion

2015

Parent fulvenes and fulvalenes are thermallyu nstable cross-conjugated olefins for which lowtemperature syntheses are indispensable. In this review 5syntheses (inthe temperature range between À 100 and À 108)are discussed:1. Reaction of sodium cyclopentadienidew ith 1-acetoxy-1-chloroalkanes or 1-acetoxy-1-bromoalkanes (26)gives acetoxy-alkyl-cyclopentadienes (27)which are easily converted to pentafulvenes (2)by low-temperature HOAc-elimination with NEt 3 .T his synthesis has been applied to parent pentafulvene (2a), heptafulvene(3a), nonafulvene (4a)a nd sesquifulvalene (19a)(Schemes 8 -11).2. Based on an early quantitative oxidative coupling of cyclononatetraenide (8)t og ive dihydrononafulvalene (38)( Scheme 10), ag eneral synthetic plan for fulvalenes has been outlined (Scheme 11)a nd applied to the synthesis of pentafulvalene (12), nonapentafulvalene (16)a nd nonafulvalene (14). Several applications of oxidative couplings of Hückel anions are discussed (Schemes 20 and 21).3. Tr ifunctional cyclopropanes 67 (inm ost cases 1,1-dibromo-2-X-cyclopropanes) are attractive precursors of parent triafulvene (1a)a nd calicene (17)(Scheme 18). Contrary to classical procedures they are transformed into nucleophiles (67 ! 68)b yh alogen-lithium exchange,m ethylation( 68 ! 69) and HBr-eliminationt og ive 1-methylidene-2-X-cyclopropaneso ft ype 71.B ys ubsequentH Xeliminationtriafulvene (1a)has been synthesized and trapped as a[4þ2]-cycloadduct 73 (Scheme 20). Furthermore,c alicene precursors 77 are available by using cyclopentenone as an electrophilic cyclopentadiene equivalent.4. Similarly,1 -lithio-1-bromo-2-X-cyclopropanes 68 are directly transformed into triafulvalene precursors 81 (Scheme 26)b yanovel CuCl 2 -catalyzed oxidative coupling.5. In view of the synthesiso fp arent triafulvene( 1a), triafulvalene( 11)a nd calicene (17), retroDielsÀAlder reactionso fs table precursors -p repared by low-temperature reactions( described in chapters 3 and 4)-have been explored.

Section: à3mentioning

confidence: 77%

“…25 )W ell-known applications: In 1958 Doering &Matzner [13] showed that cyclopentadienide (6)could be coupled by iodine to give bi(cyclopentadienyl) (42a). This reaction has been applied by Hafner et al [58] to the synthesis of various tert-butyl-substituted pentafulvalenes.F or the coupling of indenide by MarØchal [54], see Scheme 10.…”

Section: à3mentioning

confidence: 99%

Low‐Temperature Olefin Syntheses in View of Parent Fulvenes and Fulvalenes

2015

“…First synthesis of 10: [15]; a nearly quantitative coupling takes place, if 6 is reacted with AgBF, [16] NMR Spectra of nonafulvenes and nonafulvalenes will be extcnsively discussed elsewhcrc.…”

mentioning

confidence: 99%

Synthetic Attempts towards ‘Aromatic’ Nonafulvenes

Chai

1994

According to their spectroscopic behavior, four classes of nonafulvenes may be distinguished, but, so far, only three classes have been identified. Type-A nonafulvenes (including parent la) are typically olefinic molecules with strongly alternating bond lengths and a nonplanar nine-membered ring. Type-B nonafulvenes are characterized by four pairs of equivalent ring H-atoms and ring C-atoms. Spectra of both Type-A and Type-B nonafulvenes are not dependent on temperature and solvent polarity. However, spectra of Type-C nonafulvenes (including prototype Id with R' = R2 = NMe,) are strongly influenced by temperature and solvent polarity due to an equilibrium 1 p l * between the nonpolar olefinic 1 and dipolar planarized l*. So far, Type-D nonafulvenes occurring exclusively in the dipolar form l * were unknown. Synthetic attempts towards nonafulvenes of Type D are described and problems encountered in nonafulvene syntheses are discussed. Several new cyclononatetraenes and four new nonafulvenes (or nonafulvalenes) 31, In, 3, and 5 have been synthesized. Spectroscopic evidence shows that 11,12-bis(diethylamino)nonatriafulvalene 5 is the first Type-D nonafulvene.

“…Der thermisch instabile Grundkorper entzog sich jedoch einer eingehenden spektroskopischen Untersuchung. Dasselbe Verfahren wurde spater zur Synthese von Bi(cyclononatetraeny1) (8; Ausbeute 30% [5]) sowie von 1,1',3,3'-Tetra(tert-butyl)pentafulvalen und von 2,2'-Di(tert-butyl)pentafulvalen [6] angewendet. Der Mechanismus des Ringverkniipfungsschrittes 2-3 ist bisher nicht genau bekannt : Ausser einer oxidativen Kupplung ist auch eine S,'-Reaktion von Cyclopentadienid mit intennediar gebildetem 5-Iodcyclopentadien [7] Fig.…”

unclassified

“…Darauf wird 10 min bei -30" weitergeruhrt, mit cu. 5 (M=Na). UV (Hexan): 240, 300 (sh), 316 (sh), 333, 352 (sh).…”

unclassified

Synthese von Pentafulvalen durch oxidative Kupplung von Cyclopentadienid mittels Kupfer(II)‐chlorid

Escher

Rutsch

1986

Synthesis of Pentafulvalene by Oxidative Coupling of Cyclopentadienide with Copper(I1) ChlorideStarting with a nearly quantitative coupling of cyclonondtetraenide 7 to 1, 1'-dihydrononafulvalene 8 by means of AgBF,, a simple general synthetic concept for fulvalenes is outlined (Scheme 2), consisting in an oxidative coupling of 'Huckel anions' like 2 and 7 to 1, 1'-dihydrofulvalenes 10 with Ag(1) or Cu(I1) salts, followed by deprotonation (-11) and oxidation (412); it has been realised in the case ofpentafulvalene (1; overall yield 61 %; Scheme 3 ) and 1,2:5,6-dibenzopentafulvalene (18; overall yield 66%, Scheme 4 ) . NMR-spectroscopic investigations show that 1 is a non-aromatic compound with strongly alternating bond-lengths, its n-system being even more locdlised than that of simple pentafulvenes. In fact, 1 is extremely reactive in concentrated solutions above -50". Resides of polymerisations, Diets-Alder dimerisation 1 +19 followed by a rearrangement 19-20 takes place (Scheme 5 ) . 1.Einleitung. -Pentafulvalen (1) ist eine sowohl synthetisch wie theoretisch attraktive Verbindung, deren spektroskopische Daten wichtige Riickschliisse auf die n -Delokalisation und Ladungsdichteverteilung in gekreuzt konjugierten Systemen erlauben wiirden. Da 1 das n-System von Pentafulvenen aufweist, welches mit einer Butadien-Einheit iiberbriickt worden ist, konnte ein spektroskopischer Vergleich von 1 mit Pentafulvenen [ 1 J von Interesse sein.