Conjugation in bicyclo[1.1.0]butanes. LUMO properties of the bridging bond

Horner, Michael; Huenig, S.

doi:10.1021/ja00460a058

Cited by 41 publications

(29 citation statements)

References 4 publications

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“…Die zugehorige Simulation zeigt aurjerdem, darj nur bei Kopf/SchwanzDimeren die zentralen Signalgruppen die hochste Intensitat aufweisen: 2 fur AA'BB'-Isomere (r-ctt) bzw. 4 fur das A,B,-Isomere (r-fct). Diesen Spektrenhabitus beobachten wir bei allen erhaltenen Cyclobutanen C.…”

Section: Unterscheidung Von Kopnkopf-und Kopf/schwanz-lsomerenunclassified

“…255-257"C, laut 'H-NMR-Spektrum identisch mit dem aus A2,BzCI04 erzeugten Photodimeren. (22,4 I): 6.00 g (9.26 mmol) r-ctt-C8,2 Me1 werden in 50 ml Ethanol und 20 ml Wasser gelost und mit 70 ml(l.12 mol) frisch destilliertem Methyliodid und 50 ml n-Propanol versetzt. Die klare, gelbe Losung wird 48 h unter Luftausschlun bei Raumtemp.…”

Section: Epimerisierung Der Cyclobutane C8; C82 Me1 Und 22unclassified

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Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Horner

Hünig

1982

Liebigs Ann. Chem.

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Die Mono-und Diazastilbene A 1 -A 9 werden, auch als ihre Mono-und Dihydro-oder -alkylQuartirsalze, mit UV-Licht bestrahlt. Die Monosalze werden im Kristall und/oder in Losung glatt zu Cyclobutanen C dimerisiert. Die freien Basen A oder ihre Bis-Salze, die nur in Losung reagieren, bilden teilweise oder vollstlndig andere Produkte. Deren Struktur, sowie die Konstitution und Konfiguration von C1-C9 werden aufgekllrt. Literaturergebnisse werden teils bestiltigt, teils korrigiert. Pyridyl-substituted Cyclobutanes viu Photodimerisation of AzastilbenesMono-and diazastilbenes A 1 -A 9 as well as their mono-and dihydro-or -alkyl quaternary salts are irradiated (UV). Mono salts are smoothly converted into cyclobutanes C in crystalline state and/or in solution. The free bases A or their bis salts, reacting in solution only, form partly or exclusively different products. Their structures together with the constitutions and configurations of the cyclobutanes A are elucidated. Results from the literature are partly confirmed and partly corrected. ZielsetzungIn unsere Untersuchungen ilber mehrstufige reversible Redoxsysteme2) sollten auch Verbindungen einbezogen werden, die zwischen den Pyridylendgruppen das Kohlenstoffgeriist der Quadratsilure l s 3 ) oder des Bicycl~butans~*~) besitzen. Als geeignetes Ausgangsmaterial hierfiir boten sich pyridylsubstituierte Cyclobutane (,,C") an, die wiederum -wie einige Literaturbeispiele zeigens -aus den ebenfalls zum Teil bekannten Azastilbene" (,,A") durch Photodimerisierung darstellbar sein sollten. Diese Reaktionsfolge bildet, zusammen mit der Konstitutions-und Konfigurationsaufkllrung der Cyclobutane C den Inhalt der vorliegenden Abhandlung. Synthesen der Azastilbene A1 -A9Die meisten der eingesetzten Monoaza-und Diazastilbene sowie ihre Salze (vgl. Tab. I und 2) waren literaturbekannt. Sie werden im allgemeinen durch Knoevenagel-Kondensation gewonnen. Abweichungen verschiedener Darstellungsvorschriften fur AS, Me16.') aus 1,4-Dimethylpyridiniurn-iodid (1) und 4-Pyridincarbaldehyd (2) wurden zum Anial3 genommen, den EinfluD der Reaktionsdauer zu pfifen. Dabei zeigte sich eine drastische Ausbeuteverminderung mit zunehrnender Reaktionszeit; ein PhPnomen,

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Section: Unterscheidung Von Kopnkopf-und Kopf/schwanz-lsomerenunclassified

Section: Epimerisierung Der Cyclobutane C8; C82 Me1 Und 22unclassified

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Horner

Hünig

1982

Liebigs Ann. Chem.

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“…The high‐yield interconversion between 1 and 2 2+ indicates that they constitute “reversible” redox pairs, in which the bond making/breaking are induced upon ET. Furthermore, dynamic structural change upon ET causes a large separation of redox potentials of 1 and 2 2+ (Figure 2, Table 1), thus endowing the present system with high electrochemical bistability 7…”

Section: Methodsmentioning

confidence: 94%

A Redox Switch Based on Dihydro[5]helicene: Drastic Chiroptical Response Induced by Reversible C−C Bond Making/Breaking upon Electron Transfer

et al. 2001

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Helicenes are a special series of chiral molecules with huge optical activities, and thus attract considerable attention for use as nonlinear optical (NLO) materials and asymmetric catalysts. [1] Chiroptical photoswitches that function by modulating the helical geometries of helicenes by light have also been constructed. [2] However, the electron-transfer (ET) reaction of chiral helicenes has not been reported although they can serve as novel ªelectrochiropticalº transducers when redox-active groups are incorporated. We have found that dihydro[5]helicenes 1 which contain two electron-donating spiro rings undergo reversible CÀC bond breaking to give A typical synthesis procedure was as follows:Step 1: An amorphous mesoporous aluminum containing silica (Si/Al 100/1) was synthesized using SiCl 4 and AlCl 3 in ethanol, as in ref. [3]. The surfactant-containing mesoporous solid products were recovered and air-dried at room temperature.Step 2: the dried surfactant-containing mesoporous precursor was impregnated with a 10 wt % solution of TPAOH (free from inorganic alkali). The Si/TPAOH ratio was 8/1. After aging at room temperature, the solid was heated at 60 8C to eliminate water, and dried under vacuum for about 24 h at room temperature. Finally, the solid was transferred into a Teflon-lined autoclave and heated at 130 8C for different lengths of time. It is considered that the quantity of water adsorbed on the solid plays an important role in the crystallization process. Therefore, the partly crystalline solid was further crystallized at the same temperature for a given time after introducing a small amount of water. Because the solidstate crystallization continues in the presence of this small amount of water, the above process permits control of the crystallinity and the mesopore size of the solid materials. The products were washed with distilled water, dried in air at 80 8C, and finally calcined at 550 8C for 6 h to remove the organics.Characterization: Powder XRD patterns of the materials were recorded on a Philips X-ray diffractometer (PW 1010 generator and PW 1050 computerassisted goniometer) using nickel-filtered Cu Ka (l 1.5406 ) radiation, 0.0258 step size and a 1 s step time. Nitrogen adsorption and desorption isotherms at À 196 8C were established using an Omnisorp-100 apparatus. The specific surface area (S BET ) was determined from the linear part of the BET equation (P/P 0 0.05 ± 0.15). The micropore size distribution was calculated from argon adsorption isotherms with the Horva Â th ± Kawazoe method. The calculation of the mesopore-size distribution was performed using the desorption branch of the N 2 adsorption/desorption isotherms and the BJH formula. The mesopore surface area (S BJH ) and mesopore volume (V BJH ) were obtained from the pore-size distribution curves. The average mesopore diameter, d p , was calculated as 4V BJH /S BJH . Although its accuracy is limited, the BJH method, which is still universally utilized in the mesoporous molecular sieves (MMS) literature yields results that are co...

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“…Unfortunately, the crude adducts after completion of the reaction need to be purified either by traditional column chromatography or by acid–base treatment. However, if the product is sensitive towards pH or temperature then this results in a mixture of products with a change in the stereogenic center . To overcome the constrained system, the use of ditopic receptors as the catalyst has also been reported independently by MacGillivray and Wärnmark in the solid state .…”

Section: Nitrate‐anion‐promoted High‐energy Materials Synthesismentioning

confidence: 99%

“…Although the solid‐state photochemical [2+2] cycloaddition reactions worked efficiently with high stereoselectivity because of the perfect crystal‐packing effect, the main problem arises with the isolation of the pure product after completion of the reaction. The proton of the four‐membered ring is sensitive towards base and high temperature . The traditional tedious purification process gives a low yield of pure product.…”

Section: Nitrate‐anion‐promoted High‐energy Materials Synthesismentioning

confidence: 99%

Structurally Flexible C₃‐Symmetric Receptors for Molecular Recognition and Their Self‐Assembly Properties

Singh

Sun

2015

The Chemical Record

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The bioinspired design and synthesis of building blocks and their assemblies by the supramolecular approach has ever fascinated scientists to utilize such artificial systems for numerous purposes. Flexibility is a basic feature of natural systems. However, in artificial systems this is difficult to control, especially if there is no preorganization of the component(s) of a system. We have designed and synthesized a series of C3 -symmetric N-bridged flexible receptors and successfully utilized them to selectively entrap the notorious and toxic nitrate anion in aqueous medium. This was the first report of highest binding affinity for the nitrate anion in aqueous medium. An impressive self-sorting phenomenon of reversibly formed hydrogen-bonded capsules, which self-assembled from flexible tripodal receptors having branches of similar size and bearing the same amide functionality, has been disclosed. Encapsulated nitrate anion has been further utilized for the photochemical [2+2] cycloaddition reaction for the synthesis of strained four-membered ring structures through dynamic self-assembly. In this Personal Account, we summarize these results showing the utility of naturally inspired flexibility in artificial systems.

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Conjugation in bicyclo[1.1.0]butanes. LUMO properties of the bridging bond

Cited by 41 publications

References 4 publications

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

A Redox Switch Based on Dihydro[5]helicene: Drastic Chiroptical Response Induced by Reversible C−C Bond Making/Breaking upon Electron Transfer

Structurally Flexible C₃‐Symmetric Receptors for Molecular Recognition and Their Self‐Assembly Properties

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Conjugation in bicyclo[1.1.0]butanes. LUMO properties of the bridging bond

Cited by 41 publications

References 4 publications

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

A Redox Switch Based on Dihydro[5]helicene: Drastic Chiroptical Response Induced by Reversible C−C Bond Making/Breaking upon Electron Transfer

Structurally Flexible C3‐Symmetric Receptors for Molecular Recognition and Their Self‐Assembly Properties

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Product

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Structurally Flexible C₃‐Symmetric Receptors for Molecular Recognition and Their Self‐Assembly Properties