Cyclopropenonchemie, IX. Chemische und photoelektronenspektroskopische Eigenschaften von cyclopropylsubstituierten Cyclopropenonen

Abstract

Bis( 1-methylcyclopropyl)acetylen (1 a) gibt mit verschiedenen Dichlorcarben-Reagenzien Gemische des acetylenischen Ketons 3 a und des Cyclopropenons 4a, wahrend Dicyclopropylacetylen (lb) neben den analog strukturierten Verbindungen 3b und 4b zusatzlich das Produkt 10 der Aufnahme von 2CC12 (Addition und formale Einschiebung in eine C -C-Bindung) liefert. Ahnlich gebaute aliphatische Alkine sind weniger reaktiv, nur mit dem CCI,-Reagens der PhasentransferKatalyse werden nennenswerte Umsetzungen zu 12a und b sowie 13a und b erreicht. -In seiner thermischen und Hydrolysebestandigkeit liegt das cyclopropylsubstituierte Cyclopropenon 4 b zwischen Diphenylcyclopropenon und dem sehr wenig reaktiven Di-tert-hutylcyclopropenon. Dipolmomente und Basizitaten der Cyclopropenone werden zusammgefaDt ; die cyclopropyltragenden Verbindungen sind die starksten Basen. Die Photoelektronenspektren einiger Cyclopropenone wurden gemessen, der SubstituenteneinnuB auf die Ionisationspotentiale der n-und a-Elektronen wird diskutiert.Cyclopropenone Chemistry, IX la)Chemical and Photoelectron Spectroscopic Properties of Cyclopropyl-substituted cyclopropenones Bis(1-methylcyc1opropyl)acetylene (1 a) reacts with various dichlorocarbene reagents to give mixtures of acetylenic ketone 3a and cyclopropenone 4a, while dicyclopropylacetylene (1 b) gives 10 in addition to 3 b and 4 b. 10 is formed by addition plus formal insertion into a C -C-bond by 2 moles of CCI,. Aliphatic alkynes of structures similar to l a are much less reactive, only the dichlorocarbene of phase transfer catalysis leads to conversions to 12a and b, and 1311 and b. -Cyclopropyl substituted cyclopropenone 4 b is thermally and hydrolytically more stable than diphenylcyclopropenone, though less so than di-tert-butylcyclopropenone. Dipol moments and basicities of cyclopropenones are tabulated. The compounds carrying cyclopropyl groups are the most basic ones.Photoelectron spectra of some cyclopropenones were measured. The influence of substituents on the ionization potentials of n-and rr-electrons is discussed.

Three-Membered-Ring-Based Molecular Architectures

“…135a Indeed, X-ray crystal structure analyses of the derivatives 191a,b disclosed the bond between the two bicyclobutyl moieties to be shortened [1. 445(3) Å], while the central bonds in the bicyclobutane fragments were found to be lengthened [1.547(2) Å]. 135b These data are in accord with the results of DFT computations (1.456 vs 1.534 Å) 136 and indicate that these molecules in the ground state should be predisposed for reorganizations.…”

“…For 621 (R = Me), cyclopropanation under phase-transfer conditions (chloroform/conc. NaOH soln./TEBACl, method A) proved to be effective, whereas in the case of 565 (R = H), CHCl 3 /KO t Βu (method Β) was used, but the yields of the cyclopropenones 633 obtained after hydrolysis were low in both cases (Scheme ) 109 …”

“…NaOH soln./TEBACl, method A) proved to be effective, whereas in the case of 565 (R ) H), CHCl 3 / KOtΒu (method Β) was used, but the yields of the cyclopropenones 633 obtained after hydrolysis were low in both cases (Scheme 109). 445 Copper-mediated addition of ethyl diazoacetate to 565 was reported to give ethyl 2,3-dicyclopropylcyclopropene-1carboxylate (634), which could be hydrolyzed to the corresponding acid in 70-75% yield (Scheme 109). 446 Dicyclopropylethyne (565) has been converted to a number of model compounds in studies directed at comparing the influence of cyclopropyl and other alkyl or aryl substituents on the stability of, for example, vinyl cations, 447 the precursors (636 and 638) of which were prepared by addition of HCl to the correspondingly substituted cyclopropylalkynes 635.…”

Bicyclo[1.1.1]pentanes, [n]Staffanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.02,5]pentanes

“…Industrial interest in this class of compounds stems from the expectation that incorporation of 1a into a molecular structure will increase the thermal stability of the mesogen and improve its mechanical properties in a manner similar to that of some other small rings (e.g., cyclobutane). , Inspection of molecular models for 1a and other cylindrical moieties such as bicyclo[2.2.2]octane-1,4-diyl, cubane-1,4-diyl, and 1,12-dicarba- closo -dodecaborane-1,12-diyl, as well as trans- cyclohexane-1,4-diyl and 1,4-phenylene, shows that bicyclo[1.1.1]pentane is the smallest among the rings considered. The unusually short interbridgehead distance of 1.87 Å is reflected in the lowest aspect ratio ( L / D = 0.46) and negative polarizability anisotropy Δα (Table ), which are the key parameters used in classical theories describing the nematic state…”

Mechanistic and Kinetic Investigation of Liquid−Liquid Phase Transfer Catalyzed Oxidation of Benzyl Chloride to Benzaldehyde

“…Various phase transfer catalysts, such as quaternary onium salts, crown ethers, and poly(ethylene glycol)s, have been used for oxidation of alkyl and aralkyl halides and also of alcohols. Haldavanekar has reviewed the literature − on the preparation of benzaldehyde under phase transfer catalysis. A new technique of capsule membrane phase transfer catalyzed oxidation of benzaldehyde has emanated from this laboratory. − …”