Heptafulvene addition

Furthermore, the methyl-substituted triafulvenes 222 underwent Diels-Alder addition to 2-pyrone55 giving rise to heptafulvenes (510) by elimination of carbon dioxide. Extension of this reaction to other triafulvenes was unseccessful. 

A very elegant formation of heptafulvenes from triafulvenes was found by Gompper294 utilizing the push-pull stabilized cyclobutadiene 511 in the case of 1,2-diphenyl-4,4-diacetyl triafulvene (180) the 4-acyl group caused additional ring closure yielding cyclohepta(b)furan 514 ... 

In contrast to the usual (4 + 2) diene reactivity of fulvenes 3-amino fulvenes 539 in some cases are capable of expanding the five-membered ring to heptafulvenes 541 by addition of acetylene dicarboxylate in a (2 + 2) fashion299. ... 

While electrophilic reactions of alkylidenecycloproparenes are generally rapid, the nucleophilic pathways require more vigorous conditions. The only nucleophilic addition of cycloproparenes known is that of /-butoxide across the bridge bond of 237,240 and 241 which leads to the corresponding heptafulvenes 407. ... 

Prompted by W. M. Jones work on the formation of heptafulvene from phenyl-carbene in the gas phase,which implied a seven-membered ring intermediate, and by the implications of the possible reversibility of the process, Baron et al. rediscovered Vander Stouw s cryptic work and showed that all three possible tolyl-carbenes gave benzocyclobutene and styrene, albeit in different ratio from the ortho isomer than from the meta or para species.Baron et al. ° proposed a mechanism in which a methylcycloheptatrienylidene (CH3-7I) was the active seven-membered species, and which additionally feamred the intermediacy of methylbicyclo[4.1.0]-heptatrienes 73 and 73 (Scheme 7.35). 

Alkylidenecycloproparenes react slowly with nucleophiles and then only under forcing conditions140. Reactions with r-BuOK (refluxing THF, several days) provide heptafulvenes in both the benzene and naphthalene series by nucleophilic addition to the strained bridge bond and not to the exocyclic double bond (equation 36). 

Site-specific addition of diphenylnitrilimine to the C==N bond in 8-aza-heptafulvenes yields intermediate spirotriazolines, which rearrange to isomeric triazine derivatives. Proof is provided by triazine formation from an independently generated spirotriazoline sample, as shown in Scheme 28 (79CSC341 80T935). 

Using potassium tert-butoxide, alkylidenecycloproparenes reacted only under vigorous conditions via nucleophilic addition across the bridging tr-bond to give ring expanded heptafulvenes 19 101... 

The attack of the acid (154) on the readily polarizable 1,2-dithiafulvene (155) corresponds to the extremely ready addition of electrophilic reagents to the simple and vinylogous heptafulvene derivatives, which are iso-n-electronic with 155. The opening of the dithiole rings in 156 and 158 under the pressure of the carbanionoid electron pair liberated by the proton abstraction and of the free electron pair on the sulfur, as well as the elimination of elementary sulfur and the intramolecular electrophilic attack of the mercaptide ion (157) on the 5-position to form 158, are simply the typical reactions of 1,2-dithioles that have already been discussed (Section II, B, 3). The reactivity of the 3-methyl group in 154 finds many parallels in the ease of condensation of the methyl-substituted pyridinium, pyrylium, thiopyrylium, and tropylium salts, and particularly... 

Like heptafulvene itself, its 8-cyano derivatives take part as an 8tt-component in [8+2]cyclo-addition reactions, for example with acetylenedicarboxylic esters [365] or with benzyne [368]. 

Acetoxytropylium tetrafluoroborate, prepared by the addition of tropone to acetyl tetrafluoroborate, reacts with methyl-lithium and sodium cyclopentadienide to give adducts which on pyrolysis in the gas phase give heptafulvene and sesquifulvalene, respectively, in good yield. ... 

CO) 3 and to the reaction of (tropone)Fe(CO)3 with CsHg. (Tropone)Fe(CO)s reacts with A -methyltriazolinedione by 1,5-addition to give (77), characterized crystallographically, while reaction of TCNE with (heptafulvene)Fe(CO)j complexes results in [8 + 2] addition to yield adducts of structure (78). TCNE undergoes 1,3-addition to the unco-ordinated double bond of both (1- and 2-acetyl-chpt)Fe(CO)3, whereas protonation occurs at the co-ordinated double bond of the 2-acetyl derivative. Full details of the 1 1 adduct formed between (chpt)Fe(CO)s and S02 have also been reported. ... 

In addition, the same group reported on a synthesis of heptafulvenes and related seven-membered ring systems (e.g., 363) from triafulvene 357 (Scheme 7.80) [91]. A series of donor-substituted 1,3-dienes, when reacted with tria-fulvenes by a Diels-Alder addition, yielded bicyclic methylene cyclopropanes, which were subsequently transformed to 1,6-diphenyl-substituted heptafulvenes or seven-membered ring derivatives. 

Cycloalkenylcarbenes are carbenes that contain a cyclic side group. Tolane is the major decomposition product from the decomposition of diphenylcyclopropene diazomethane and a minor product is formed via normal ring expansion (Scheme 22). Cycloheptatrienylcarbene yields only benzene, acetylene, and heptafulvene in addition to cyclooctatetraene (Scheme 23). 

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