Semibullvalene synthesis

Efficient syntheses of substituted succinic acids have been developed in the past [42] a more recent application is the coupling of 13 as part of a semibullvalene synthesis [43]. While ketocarboxylic acids can be dimerized satisfactorily (Table 2), the corresponding aldehydes couple poorly. However, good yields can be obtained in these cases when the acetals, e.g. 14 [44], are electrolyzed instead. 

The synthesis of an optically active semibullvalene has been realized for the first time Sequential reaction of methylcyclooctatetraene with one equivalent each of bromine and (—)-e/Kfo-bomyltriazolinedione gave a mixture of Diels-Alder adducts which when debrominated afforded 362. Photocyclization to bishomocubane 363 allowed for chromatographic separation of the two diastereomers. Silver ion-... 

From a purely synthetic viewpoint, triazolinedione adducts have served as substrates for gaining access to numerous target molecules such as prismane, semibullvalene, bridged semibullvalenes, elassovalene, caged compounds, and azoalkanes. Indeed, the title reagent can be used not only as a chiral source, but also as an azo donor. In the synthesis of 4,5-diazatwis-4-ene, for example, (-)- nfirst step involved cycloaddition to cyclooctatetraene dibromide with formation of a separable mixture of diastereoisomers. Eventual removal of the... 

Most reactions in this category are due to the interest in molecules like semibullvalene. The Paquette synthesis" of the parent compound takes advantage of an easy 1,5-... 

In the early seventies Stork and his students have shown that the intermediate enolate can be trapped by suitable electrophiles, e.g. alkyl halides, giving substituted ring-opened products. These modes of cyclopropane opening have been used for the synthesis of several natural compounds ". A tetra-activated cyclopropane is cleaved by sodium naphthalene in a preparation of a specifkally substituted semibullvalene (equation 36) . ... 

X = CH or CPh) electrocyclic cleavage is more commonly observed. Of such examples the domino-Diels-Alder-like synthesis of semibullvalenes deserves... 

Synthesis of Semibullvalene (5) by Vapor-Phase Irradiation of Cyclooctatetraene (4) Typical Procedure 126... 

Sauer et al. reported a one-pot synthesis of a series of semibullvalenes 164 starting from 3,6-disubstituted-l,2,4,5-tetrazines 1 and 1,1 -dimethyl-1,1 -bi(cycloprop-2-ene) 161. A plausible mechanistic explanation for the overall reaction consists of [4-1-2] cycloaddition to give the -isomer of diazanorcaradiene 162. Upon ir /7-ry -isomeriza-tion, another [4-1-2] cycloaddition leads to the final product 164. In the case of aryl substituents, which weaken the tendency for a-ry -isomerization, the corresponding 2,5-diaryldiazanorcaradienes 163 were isolated as the early intermediates in this reaction sequence (Scheme 43) <2002EJ0791>. 

Scheme 4.7 Synthesis of semibullvalene 2,4,6,8-tetracarboxylic acid ester...

Scheme 4.11 Synthesis of 2,4,6,8-semibullvalene tetracaiboxylic acid anhydride...

Quast H, Carlsen J, Janiak R et al (1992) Synthesis and X-ray diffraction analysis of Bis (phenylsulphonyl) semibullvalenes. lifting of the degentaacy of semibullvalenes in the crystal lattice. Chem Ber 125 955-968... 

Wang C, Yuan J, Li G et al (2006) Metal-Mediated efficient synthesis structural characterization and skeletal rearrangement of octasubstituted semibullvalenes. J Am Chem Soc 128 4564-4565... 

Miller LS, Grohmann K, Dannenberg JJ et al (1981) Semibullvalenes. 1. synthesis and crystal strucmre of 1,5-Dimethyl- 2,4,6,8-tetrakis (carbomethoxy) tricyclo-[3.3.0.0 ] octa-3,6-diene-A donor- acceptor- substituted semibullvalene. J Am Chem Soc 103 6862-6865... 

In 1971, based on the theoretical study, Dewar predicted that the introduction of heteroatoms like nitrogen into the semibullvalene skeleton (e.g., 2,6-dia-zasemibuUvalene, NSBV) could further reduce or even eliminate the barrier of the Cope rearrangement and thus result in a delocalized, homoaromatic ground state [16]. However, the difficulties in the synthesis, isolation, and structural characterization of NSBV hampered chemists to find an experimental probe as real model to prove the theoretical assumption. In 1982, Mullen reported the only experimental... 

Bullvalene (Figure 10) is a molecule that was predicted to undergo rapid degenerate Cope rearrangement 63). This hypothesis was only testable once the synthesis of bullvalene had been achieved (64). At 100 °C the NMR-spectnun of bullvalene exhibits a most remarkable property, viz. only one sharp resonance X = 5.8. On cooling, this band broadens. At -25 °C, two bands are apparent, one centered at x = 4.0 with relative area 6, the other centered at x = 7.9 with a relative area of 4. Semibullvalene has analogous properties (65). 

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