Oxidative transformations of cembrane diterpenoids III. Epoxycembrenes
Summary1. It has been established that the epoxidation of cembrene with perbenzoic and peracetic acids takes place stereospecifically at each of the trisubstituted double bonds with the formation of 4S,5R-, 7S,8S-, and 11S,12S-monoepoxycembrenes, the structures and absolute configurations of which have been established by spectral methods.2. Epoxidation of cembrene at the C11–C12 double bonds under the conditions used takes place preferentially as compared with epoxidation at the C7–C8 double bond.
Organic reactions in a solid matrixI , , Alumina-induced oxirane rearrangements
Abstract A fairly generation transformation of methyldialkyl-substituted 1,2-epoxides to the corresponding vinylidene, allylic secondary alcohols, on contact with active Al2O3, is described. A systematic study of some of the reaction variables of this transformation has also been carried out. The epoxides thus studied include those derived from the following olefins: 1-methylcyclopentene, 1-methylcyclohexene, 1-methylcycloheptene, α-pinene and Δ3-carene.
Unidirectional hexagonal rare-earth disilicide nanowires on vicinal Si(100)-2×1
Rare-earth disilicide nanowires grown on vicinal Si(100) with a miscut of 2–2.5° toward the [110] azimuth at 600 °C were studied by scanning tunneling microscopy and compared with those grown on flat Si(001). In contrast to rare-earth disilicide nanowires grown on flat Si(100) surfaces, the nanowires grow unidirectionally along the [01̄1] direction of the vicinal Si(100) surface. Rare-earth disilicide nanowires form bundles composed of single nanowire units on both flat and vicinal surfaces. Yet, on the vicinal surface, the bundle width is comparable to the width of the terrace. The average nanowire length on the vicinal substrate is longer than that on the flat substrate. Scanning tunneling spectroscopy shows that the rare-earth disilicide nanowires have metallic properties.