Reactions of diterpenoids on solid supports II. Behavior of di- and tricyclic diterpenoids on alumina containing oxidants

The behavior of epimanool (1), epimanool oil, larixol (2), cis-abienol (3) and methyl dehydroabietate (4) on alumina impregnated with oxidants (H₂CrO₄ and KMnO₄) has been studied. This has led to the methyl ketone (5) and norambrenolide (8) - precursors of the perfume substances 14,15,17-trinorlabdane-8,13-dione (6), 8-hydroxy-14,15-bisnorlabd-II-en-13-one (7), and methyl 7-oxodehydroabietate (14). -Levantenolide (11) has been synthesized in one stage from cis-abienol (3)for the first time.Novosibirsk Insitute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 229–234, March-April, 1995. Original article submitted July 25, 1994.     

Determination of enthalpies of formation of organic free radicals from bond dissociation energies 2. Halosubstituted radicals

The enthalpies of formation (ΔH _f ^o) for 23 halosubstituted radicals were determined from the published data on bond dissociation energies. The ΔH _f ^o values of the corresponding molecules necessary for the calculation of ΔH _f ^o of the radicals were taken from handbooks or calculated by the additive-group method. The conjugation energies of the radicals are calculated, and the effect of substituents at the π-system on these values was shown. Errors of determination of the ΔH _f ^o values of the radicals were estimated. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 643–646, April, 1998.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXVIII. Effect of the Nature of the Verdazyl Indicator on Salt Effects in Dehydrobromination of 3-Bromocyclohexene in Nitrobenzene

The salt effect on the rate of dehydrobromination of 3-bromocyclohexene in PhNO2 depends on the nature of the verdazyl indicator. With triphenylverdazyl and its chloro and nitro derivatives in the presence of Et₄NClO₄, a normal salt effect is observed, in the presence of bromides, a superposition of normal and special salt effects, while in the presence of chlorides, a superposition of normal and special negative salt effects. With the dimethoxy verdazyl derivative, a normal salt effect is always observed.     

Simultaneous comparison of δ31P and 1JPN for the assignment of E/Z-stereochemistry of the phosphorus-nitrogen double bond in iminophosphines R-P=N-R′

 The analysis of ³¹P and ¹⁵N NMR data of a series of 40 iminophosphines R-P=N-R′ reveals that the E/Z-stereochemistry of the PN double bond can be predicted on the basis of a simultaneous comparison of the values of δ³¹P and ¹J_PN. Received: 31 May 1996/Revised: 2 July 1996/Accepted: 5 July 1996     

Uranextraktion mit Triphenylarsinoxid

Analytical and Bioanalytical Chemistry - Es wird eine neue extraktive Trennungsmethode für Uran beschrieben. Mit Hilfe einer Lösung von Triphenylarsinoxid in Chloroform lassen sich...