The Photochemistry of 5,6‐Dimethylidene‐2‐norborananone. Synthesis and <i>Diels‐Alder</i> Reactivity of 2,3‐Dimethylidenebicyclo‐[2.1.1]hexane

Schwager, Luis; Vogel, Pierre

doi:10.1002/hlca.19800630508

Cited by 10 publications

(2 citation statements)

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“…It furnishes a 3:2 mixture of adducts 12 and 13; 12 was obtained pure by fractional recrystallization. [24] serve to generate bicyclo[2.1.l]hex-Zene systems. With maleic anhydride, the adduct 15 was formed whose crystallization failed to give suitable crystals for X-ray diffraction analysis.…”

Section: Discussionmentioning

confidence: 99%

The Non‐planarity of the Bicyclo[2.2.1]hept‐2‐ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct‐2‐ene, Bicyclo[2.2.1]hept‐2‐ene, and Bicyclo[2.1.1]hex‐2‐ene Systems

Pinkerton¹,

Schwarzenbach²,

Birbaum

et al. 1984

Helvetica Chimica Acta

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SummaryThe crystal structures of (1 R,4R,5S,8S)-9,l0-dimethylidenetricyclo[6.2.1 .02.7]undec-2(7)-ene-4,5-dicarboxylic anhydride (3), (1 R,4R,5S,8S)-1 1-isopropylidene-9,lO-dimethylidenetricyclo(6.2.1 .02~7]undec-2(7)-ene-4,5-dicarboxylic anhydride (6), (1 R,4R,5S,8S)-9,l O-dimethylidenetricyclo[6.2.2.O2~7]dodec-2(7)-ene-4,5-dicarboxylic anhydride (9), (1R,4R,5S,8S)-tricyclo[6.2.2.02~7]dodeca-2(7), 9-diene-4,5-dicarboxylic anhydride (12) and (4R,SS)-tricyclo[6.1. 1.02~7]dec-2(7)-ene-4,5-dicarboxylic acid (16) were established by X-ray diffraction. The alkyl substituents onto the endocyclic bicyclo[2.2.l]hept-2-ene double bond deviate from the C(1), C(2), C(3), C(4) plane by 13.5" in 3 and by 13.9" in 6, leaning toward the endo-face. No such out-of-plane deformations were observed with the bicyclo[2.2.2]oct-2-ene derivatives 9 and 12. The exocyclic s-cis-butadiene moieties in 3, 6 and 9 do not deviate significantly from planarity. The deviation from planarity of the double bond in bicycl0[2.2.l]hept-Zene derivatives and planarity in bicyclo[2.2.2]oct-2-ene analogues is shown to be general by analysis of all known structures in the Cambridge Crystdographic Data File. The non-planarity of the bicycl0[2.2.l]hept-2-ene double bond cannot be attributed only to bond-angle deformations which would favour rehybridization of the olefinic C-atoms since the double bond in the more strained bicyclo[2.l.l]hex-2-ene derivative 16 deviates from planarity by less than 4".

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Section: Discussionmentioning

confidence: 99%

The Non‐planarity of the Bicyclo[2.2.1]hept‐2‐ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct‐2‐ene, Bicyclo[2.2.1]hept‐2‐ene, and Bicyclo[2.1.1]hex‐2‐ene Systems

Pinkerton¹,

Schwarzenbach²,

Birbaum

et al. 1984

Helvetica Chimica Acta

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“…2.3 and 2.2 , respectively), the 1 H NMR NMR chemical shift of the bridgehead proton should reflect the tropicity of the annelated p-conjugated ring to the same extent. In fact, the signal of the bridgehead protons in benzene 3 (d = 3.21 ppm) [6] showed a downfield shift from that of the reference compounds bicycloA C H T U N G T R E N N U N G [2.1.1]hexene (12) [23] or 2,3-dimethylenebicycloA C H T U N G T R E N N U N G [2.1.1]hexane (13; d = 2.54 and 2.95 ppm, respectively), [24] in a similar extent to the shift obwww.chemeurj.org served for benzene 5. This finding is consistent with the results of the theoretical calculations for the NICS (GIAO-HF/6-31 + GA C H T U N G T R E N N U N G (d,p)//B3 LYP/6-31G(d)) of 3 (À8.0 ppm), which is large negative value that is rather close to the value of the parent benzene (À9.7 ppm), [6] and for the CTOCD method, which indicates the presence of a strong diatropic ring current.…”

Section: Resultsmentioning

confidence: 99%

Antiaromaticity and Reactivity of a Planar Cyclooctatetraene Fully Annelated with Bicyclo[2.1.1]hexane Units

Nishinaga

Uto

Inoue

et al. 2008

Chemistry A European J

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A detailed investigation has been made into the antiaromaticity and chemical reactivity of a planar cyclooctatetraene (COT) molecule fully annelated with bicyclo[2.1.1]hexane units 2. In spite of its planar 8pi-electronic structure, theoretical calculations have indicated that the antiaromaticity of COT 2 is considerably decreased in comparison with a planar COT 16 with D 4h symmetry. This behavior appears to be related to the wider HOMO-LUMO gap of 2 relative to 16, which is caused by the raised LUMO level as a result of the effective sigma-pi* orbital interaction between the strained bicyclic framework and the COT pi system. The two-electron reduction of 2 required the use of potassium mirror or a combination of lithium/corannulene in highly dried [D8]THF at -78 degrees C under vacuum. In contrast, the [4+2] cycloaddition of 2 with tetracyanoethylene (TCNE) proceeded quite smoothly owing to the high-lying HOMO. Reaction of 2 with meta-chloroperbenzoic acid gave all-trans tetraepoxide 23 in the same way as the corresponding benzene derivative 3. While the Simons-Smith-type cyclopropanation of benzene 3 gave tricyclopropanated derivative 21, the reaction of 2 only afforded isomers of dicyclopropanated derivatives 25 and 26. Yet, the reactivity of 2 is higher than the parent COT, which does not show any reactivity under the same conditions. On the basis of homodesmic reactions, it was concluded that release of strain is also an important factor for such relatively high reactivity in the epoxidation and cyclopropanation of bicycloannelated COT 2 as well as benzene 3.

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3,4‐Bismethylentricyclo[3.1.0.0]hexan — Synthese und Diels‐Alder‐Addition an Tetracyanethylen

Lanzendörfer

Christl

1983

Angewandte Chemie

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boramethylencyclopropans[3 1 2 auszuschlieBen. FOr die B-Atome erscheinen unterhalb-11°C zwei Signale bei 6-52 und 18, die gegenfiber denen von Trialkylboranen (8 11 B .... 80) deutlicb zu hohem Feld verschoben sind. Hochfeldverschiebungen sind charakteristisch fOr sp-bybridisierte Boratome: fUr Iminoborane wurden Signale bei 8-2-13 gefunden[4 1. Wir ordnen daher das Signal bei 6-18 dem B-Atom der C-B-Bindung zu; die Hochfeldverschiebung fUr das B-Atom im Dreiring wird vermutlich durch Konjugation mit der Ooppelbindung bewirkt. Auch fUr die tert-Butylgruppen Cindet man im IH-NMR-Spektrum unterhalb-47°C, im 13C-NMR-Spektrum unterhalb-30•C je zwei Signale im Intensitlitsverhiiltnis 1 : 1. Temperaturerh6hung fUhrt bei diesen sowie bei den Signalen der Boratome uber Linienverbreiterung m Koaleszenz und Linienverschiirfung. Fur die beiden Trimethylsilylgruppen erscheint hingegen zwischen-100 und +25•C im 1H_, 13C_ und 29Si-NMR-Spektrum nur ein scharfes Signal. Aus den Koaleszenztemperaturen (-47,-30 bzw.-11 DC fUr IH, 13C bzw. I1B) und den zugehOrigen Verschiebungsdifferenzen tesultiert eine Energiebarriere von 11.4 keal/mol, die wir der Topomerisierung von 3 durch Dibora-methylencyc1opropanumlagerung zuordnen. 3 weist im Raman-Spektrum zwei Banden bei 1675 und 1715 cm-I im Intensitlltsverhiiltnis 4: 1 auf, die wir den Valenzschwingungen I1B_C bzw. IOB_C zuordnen.

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The Photochemistry of 5,6‐Dimethylidene‐2‐norborananone. Synthesis and Diels‐Alder Reactivity of 2,3‐Dimethylidenebicyclo‐[2.1.1]hexane

Cited by 10 publications

References 50 publications

The Non‐planarity of the Bicyclo[2.2.1]hept‐2‐ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct‐2‐ene, Bicyclo[2.2.1]hept‐2‐ene, and Bicyclo[2.1.1]hex‐2‐ene Systems

The Non‐planarity of the Bicyclo[2.2.1]hept‐2‐ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct‐2‐ene, Bicyclo[2.2.1]hept‐2‐ene, and Bicyclo[2.1.1]hex‐2‐ene Systems

Antiaromaticity and Reactivity of a Planar Cyclooctatetraene Fully Annelated with Bicyclo[2.1.1]hexane Units

3,4‐Bismethylentricyclo[3.1.0.0]hexan — Synthese und Diels‐Alder‐Addition an Tetracyanethylen

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