42604-04-6Relevant articles and documents
SINGLET PHOTOSENSITIZATION OF SIMPLE ALKENES. PART 4. CIS-TRANS PHOTOISOMERIZATION OF CYCLOHEPTENE SENSITIZED BY AROMATIC ESTERS. SOME ASPECTS OF THE CHEMISTRY OF TRANS-CYCLOHEPTENE
Inoue, Yoshihisa,Ueoka, Toshihiko,Kuroda, Takayuki,Hakushi, Tadao
, p. 983 - 988 (1983)
Upon photosensitization at -78 deg C of cis-cycloheptene (1c) with methyl benzoate as sensitizer, trans-cycloheptene (1t) was produced in a high trans:cis photostationary ratio of 0.24. trans-Cycloheptene thus formed was entirely stable at -78 deg C and, on warming to room temperature, regenerated the cis-isomer quantitatively, but was found to be trapped efficiently by methanol in acid and by diazomethane at low temperature.An anomalous enhancement of the rate of proportionation was observed for (1t) compared with (1c) or even with trans-cyclo-octene, for which the constrained structure of (1t) must be responsible.The thermodinamic parameters for the thermal trans-cis isomerization of (1t) were also determined from a study of the lifetime at temperatures between -15.0 and +1.0 deg C:Ea 17.4 kcal mol-1,(*) log A 11.1, ΔG(*)266 19.4 kcal mol-1, ΔH(*)266 17.0 kcal mol-1, ΔS(*)266 -9 cal K-1 mol-1.A potential energy curve for the ground-state cycloheptene was presented.
Oxidation of Alkyl Phenyl Selenides, Tellurides, and Telluroxides with meta-Chloroperbenzoic Acid for a Facile and Novel Transformation of C-Se and C-Te Bonds to C-O Bonds
Uemura, Sakae,Fukuzawa, Shin-ichi
, p. 471 - 480 (2007/10/02)
In sharp contrast to the well-known selenoxide elimination leading to olefins, the treatment of alkyl phenyl selenides (PhSeR) with an excess of meta-chloroperbenzoic acid (MCPBA; 2-5 equiv. to a selenide) in alcohol at room temperature affords the corresponding dialkyl ethers by the substitution of a phenylselenium (PhSe) moiety with an alkoxy group.A similar reaction proceeds by using alkyl phenyl tellurides (PhTeR) and telluroxides , a facile substitution of PhTe or PhTe(O) moiety by an alkoxy group being observed.Methanol is the most appropriate solvent for these oxidations and alkyl methyl ethers are formed in excellent yields.The reaction is accompanied by phenyl migration when applied to some selenides, tellurides, and telluroxides having a phenyl group at a vicinal position to the PhSe, PhTe, or PhTe(O) moiety.Application to the methoxyselenation and methoxytelluration products of cyclohexene and cycloheptene results in a ring-contraction to afford the dimethyl acetals of cyclopentane- and cyclohexane-carbaldehyde, respectively.In case of an allylic phenyl selenide, a sigmatropic rearrangement giving a rearranged allylic alcohol occurs in much preference to the substitution by the methoxy group.Other oxidizing agents than MCPBA such as NaIO4, H2O2, t-BuOOH, and ozone are generally ineffective under similar conditions.It is proposed that the reaction mainly takes place as follows.Alkyl phenyl selenone, alkyl phenyl tellurone, or the MCPBA addition product to them is formed as a reactive intermediate in which an alkyl C-Se or alkyl C-Te bond fission occurs heterolytically by a nucleophilic attack of alcohol, sometimes accompanied by a 1,2-shift of the β-substituent, i.e., phenyl migration and ring-contraction.
MASSENSPEKTREN ALICYCLISCHER VERBINDUNGEN, VIII; trans-1-BROM-2-HYDROXYCYCLOALKANE UND trans-1-BROM-2-METHOXYCYCLOALKANE
Remane, H.,Haufe, G.
, p. 145 - 154 (2007/10/02)
Die massenspektrometrische Fragmentierung der trans-1-Brom-2-hydroxycycloalkane und der trans-1-Brom-2-methoxycycloalkane der Ringgroessen C5 bis C8 und C12 wird diskutiert und mit der Fragmentierung der Bromcycloalkane, der Hydroxycycloalkane bzw. der Methoxycycloalkane gleicher Ringgroesse verglichen.Die dominierenden Zerfallsreaktionen sind einmal die Abspaltung der funktionellen Gruppen unter Bildung der Fragmente M-H2O, M-HOCH3 bzw.M-Br.Zum anderen der Abbau des Rings unter Bildung der Fragmente C3H4X (X=Br, OH, OCH3).Die Intensitaeten der wichstigten Fragmente zeigen eine deutliche Abhaengigkeit von der Ringgroesse.Die Unterschiede in den Intensitaeten von cis- und von trans-1-Brom-2-hydroxycyclododecan sowie von cis- und von trans-1-Brom-2-methoxycyclododecan erlauben die prinzipielle Unterscheidung der Isomeren an Hand ihrer Massenspektren.Aus dem Vergleich der Fragmentierung der bifunktionellen 1-Brom-2-hydroxycycloalkane bzw. der 1-Brom-2-methoxycycloalkane mit der Fragmentierung der monofunktionellen Verbidungen kann der Schluss gezogen werden, dass sich die funktionellen Gruppen beim massenspektrometrischen Abbau beeinflussen.
