Synthese und Struktur von 2,6‐Dicyanbicyclo[3.3.1]nona‐2,6‐dienen und 2,6‐Dicyanbarbaralanen

Abstract

Zinkiodid-katalysierte Addition von Trimethylsilylcyanid anThe zinc iodide-catalyzed addition of trimethylsilyl cyanide to bicyclo[3.3.l]nonane-2,6-dione (5) yields the sterically defined 0-silylated cyanohydrin 9. Trichlorophosphane oxide in pyridine converts the latter to the unsaturated dinitrile 7c. Depending on the amount of N-bromosuccinimide used, the bromination of the dinitrile 7c affords either a mixture of the monobromo-(10) and the dibromodinitrile 7 d or pure dibromodinitrile 7d. With sodium methoxide in methanol the monobromodinitrile 10 is converted ilia a concerted dehydrobromination to 2.6-dicyanobarbaralane (8c) The latter is formed almost quantitatively on debromination of the dibromodinitrile 7 d with zinc/copper reagent, while sodium methoxide yields the 4-bromo-2,6-dicyanobarbaralane (12). All reactions proceed smoothly in high yields. X-ray analyses reveal the exo-configuration of the bromine atoms in 7 d and 10. X-ray structural parameters for bicyclo[3.3.l]nona-2,6-dienes (i. e. 7c, d and 10) and a barbaralane (i. e. 12) have for the first time become available.Wahrend nach Winstein 2, im Grundzustand homoaromatischer Molekiile und Ionen 3) eine stabilisierende transannulare konjugative Wechselwirkung von (4n + 2) x-Elektronen besteht, die aus einem System oder mehreren Teilsystemen mit jeweils gerader Elektronenzahl stammen ("closed-shell"-Systeme), lafit sich der Ubergangszustand 2 der entarteten Cope-Umlagerung von 0 Verlag

The Search for Bishomoaromatic Semibullvalenes and Barbaralanes: Computational Evidence of Their Identification by UV/Vis and IR Spectroscopy and Prediction of the Existence of a Blue Bishomoaromatic Semibullvalene

“…35 j Solution in chloroform. 35 k Solution in dichloromethane. 24 However, the calculations find that the methyl groups at the bridgehead carbons, C-1 and C-5, prevent maximal stabilization of 1f deloc by the phenyl groups at C-4 and C-8 by forcing the phenyls to twist out of conjugation (by 42°) with the 2p-π AOs at these carbons.…”

Homoconjugation vs. Exciton Coupling in Chiral α,β-Unsaturated Bicyclo[3.3.1]nonane Dinitrile and Carboxylic Acids

“…Difunctional α,β-unsaturated nitrile 3 and acid 4 (Scheme 1) were prepared using the typical synthetic methodology, which involves sequential dehydration of ketone cyanohydrins using phosphorus oxychloride/pyridine or thionyl chloride, followed by acidic or alkaline hydrolysis of the resulting conjugated nitrile. Quast et al [17] used this method for the synthesis of bicyclo[3.3.1]nona-2,6-diene-2,6-dicarbonitrile and 2,6-dicyanobarbaralanes from the racemic bicyclo[3.3.1]nonane-2,6-dione 1 . Herein we report on the synthesis of enantiomerically pure dinitrile 3 from (+)-( 1S,5S )-bicyclo[3.3.1]nonane-2,6-dione ( 1 ) (Scheme 1).…”

“…NaHCO 3 and dried over Na 2 SO 4 . The residue was purified by column chromatography (eluent ethyl acetate/petroleum ether, 1:3) to yield 3 (186 mg, 71%) as colorless crystals; mp 147–149 °C (racemate mp 189–190 °C [17]); [α] D = +15.5 ( c 0.71, CHCl 3 ); UV, λ max (logε): 201 (4.24); IR (KBr) ν max /cm −1 2919, 2208, 1628, 1433; 1 H-NMR (CDCl 3 , ppm) δ 6.62 (dd, J = 5.0, 2.5 Hz, 2H), 2.84–2.67 (m, 2H), 2.55–2.26 (m, 4H), 1.80 (t, J = 3.2 Hz, 2H); 13 C-NMR (CDCl 3 , ppm) δ 142.6, 118.6, 116.2, 31.0, 29.0, 26.6; Anal. Calcd for C 11 H 10 N 2 : C 77.62; H 5.92; N 16.46.…”

Synthesis and Structure of C2-Symmetric, Doubly Bridged Bis(indenyl)titanium and -zirconium Dichlorides

“…We based our successful synthesis of the bicyclic-bridged 19 on the bis-Nazarov approach applied above for the preparation of 9 . We prepared racemic Meerwein's diketone 12 and converted it into the dinitrile 13 according to literature procedures . We were unable to get good yields of the desired dibenzoyl compound 15 by the direct addition of phenyllithium or phenylmagnesium halides to the nitriles.…”

“…Bicyclo[3.3.1]nona-2,6-diene-2,6-dicarboxaldehyde (14). Bicyclo[3.3.1]nona-2,6-diene-2,6-dicarbonitrile ( 13 ) was prepared according to the literature from Meerwein's diketone 12 . To a solution of 13 (8.6 g, 50.5 mmol) in benzene (500 mL) at −78 °C was added diisobutylaluminum hydride (1.5 M in toluene, 86 mL, 129 mmol) dropwise.…”