cis-2,3-Di-tert-butylcyclopropanones

The preparation of the strained cis-2,3-di-tert-butylcyclopropanone 2 from the acyclic compound, α,α′-dibromodineopentyl ketone 1, using a previously reported methodology, is dramatic evidence of both the existence of oxyallyl intermediates in the mechanism of this reaction, and of the integrity with which oxyallyls ring-close to cyclopropanones by a disrotatory route. Because of the bulky cis substituents, cyclopropanone 2 exhibits a number of unusual spectroscopic features (as compared to the trans isomer 5). With the aid of ab initio calculations on 2 and 5, it can be shown that the C2—C3 bond in 2 interacts with the carbonyl π-orbitals, thus causing the carbonyl oxygen to bend 12° out of the plane; this interaction is absent in 5 and the latter has a planar carbonyl group. As with other cyclopropanones, 2 can be photochemically decarbonylated. This process itself appears to be stereospecific even though highly strained alkenes are produced. Cyclopropanone 2 is thermally rearranged to the trans isomer 5 and the kinetics for this are reported; our favoured mechanism involves oxyallyl intermediates. Other reactions of 2 also appear to proceed through these oxyallyl species; for example, alcohols initially add to 2 to give α-alkoxy ends, solutions of 2 enter into very facile diene cycloadditions, and the dimerization of neat 2 also appears to involve these oxyallyl species. Keywords: cyclopropanones, oxyallyl, stereomutation, stereospecific decarbonylation, nonplanar carbonyl.

A Novel Halogenated Compound Possessing Antibiotic and Cytotoxic Activities Isolated from the Fungus Resinicium pinicola (J. Erikss.) Erikss. & Hjortst

Pinicoloform, a novel unbranched acyclic compound containing a trichloromethyl group, has been isolated from extracts of the mycelia of the Basidiomycete Resinicium pinicola. It was isolated because of its ability to induce morphological and physiological differentiation of mammalian cells, although it also exhibits antibiotic and cytotoxic activities. The structure of pinicoloform was determined by spectroscopic methods.

Synthesen und Strukturen sechsgliedriger Cyclometallaphosphazene von Tellur(IV) und Rhenium(VII) / Syntheses and Structures of Six-Membered Cyclometallaphosphazenes Containing Tellurium(IV) and Rhenium(VII)

The reactions of the tridentate ligands (Me3Si)2NC(4-RC6H4)NPPh,NSiMe3 [(1): R=H, (2): R=CF3] with Re2O7 yield the six-membered rings , (4): R=CF3]. The acyclic compound Me3SiNC(4-CF3C6H4)NPPh2NReO2OSiMe3 (5) has been obtained by reaction of 2 with Me3SiOReO3- 2 reacts quantitatively with TeCl4 to form the metallacycle . The molecular structures of 4·CH2Cl2 and 6 · pyridine · 0.5 toluene have been determined by X-ray diffraction.