Bis(dirnethylphenylsi1yl)copper-lithium (1 ) reacts with hex-1 -yne, propyne, acetylene itself, phenylacetylene, and hex-3-yne to give the products of syn addition of the dimethylphenylsilyl group and the copper. The resultant vinylcopper reagents react with a variety of electrophiles, such as the prot.on, iodine, acyl and alkyl halides, enones, and epoxides, to give vinylsilanes. With the terminal alkynes, the silyl group becomes attached with a high level of regioselectivity to the terminal carbon atom, with the result that the final products are 2,2-disubstituted vinylsilanes. VINYLSILANES now occupy an established place inReaction OJ the Silylcuprate Reagent (1) with Acetylenes. organic synthesis, because they often react with electro--Dimethylphenylsilyl-lithium is easier to make than philes regio-and stereo-specifically,l and because their trimethylsilyl-lithium and we have used it throughout epoxides are masked aldehydes or ketones.2 However, in this work. We have no reason to expect the phenyl there are not many ways of preparing 2,e-disubstituted group to interfere seriously with the vinylsilane chemisvinylsilanes.3 In a preliminary comm~nication,~ we try which one might want to do subsequently. We find reported that our silylcuprate reagent (1) reacted with that the reagent ( l ) , prepared by mixing 2 mol equiv. of (Me, PhSi ),CuLi*LiCN / / \ \ terminal acetylenes, and the intermediate vinylcopper dimethylphenylsilyl-lithium with 1 mol equiv. of coppercompounds ( Z ) , (7), and (9) then reacted with the stan-(I) cyanide, reacts with hex-1-yne to give a vinylcopper dard electrophiles of organocopper chemistry to give species (2). When we quenched this intermediate with 2,2-disubstituted vinylsilanes (3), (8), and (10). We now water, we obtained only [>99% (by g.1.c. and lH n.m.r.)] report our work in full, and include further examples the vinylsilane (3a) in 94% yield based on the acetylene. establishing the scope of this easy vinylsilane synthesis. The silylcuprate reagent (1) had not removed the proton from the hexyne, as alkylcopper reagents do; this was t No reprints available.

Systematic studies of mass transfer interactions with intrinsic reaction kinetics were performed for the threephase selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) over a modified Pd/CaCO 3 catalyst under solvent free conditions. Hydrogen concentration in the liquid phase (C H2,b ) was monitored in situ during the catalytic reaction by means of the "Fugatron" analyzer. Reactions were carried out in an autoclave at different stirring rates at two concentrations of hydrogen (5 and 13 mol · m -3 ). For stirring speeds higher than 1500 rpm no influence of gas-liquid mass transfer was observed. Hydrogen liquid-solid (L-S) mass transfer was found to be negligible, whereas the MBY mass L-S transfer becomes important at high MBY conversions at high hydrogen concentration. Low stirrer speed caused the reaction rate and MBE selectivity to decrease. No internal mass transfer limitations were observed, and conditions for the kinetic regime were found. The kinetics modeled followed the Langmuir-Hinshelwood mechanism and was consistent with the experimental data.

Catalytic hydrogenation in the liquid phase is a very common reaction type in the production of fine chemicals and pharmaceuticals. Among the various reaction techniques, it is the slurry technique (stirred tank or venturi type loop reactor) in a semi-batch mode which is most frequently used. General safety aspects of catalytic hydrogenations will be discussed und exemplified for a typical three-phase semi-batch catalytic hydrogenation.

A new instrument, the Fugatron, is presented that was developed to make in situ measurements of dissolved hydrogen concentrations in laboratory reactors. The principle of measurement is based on a probe with a tip that consists of a small porous metal substrate coated with a dense layer of fluoropolymer. The probe is exposed to the liquid phase and is internally purged by a constant flow of carrier gas. Driven by the hydrogen concentration gradient between the external and internal side of the composite layer, the hydrogen molecules permeate into the carrier gas stream. The concentration of the permeate in the carrier gas stream is measured by a gas analyzer. The analyzer signal is proportional to the partial pressure of dissolved gas. The steady-state concentration of dissolved hydrogen in the liquid is calculated from the analyzer signal by using solubility data. Calibration methods are described for immersion probes used for in situ measurements in reactors which are operated in batch or continuous mode as well as for flow-through probes used for liquid stream analysis. The sensitivity of the instrument and the reliability of the measurements were tested in different solutions as a function of temperature and pressure. The hydrogenation of an alkyne with a suspended palladium catalyst was chosen as a model reaction for in situ measurements. The hydrogenation experiments were carried out in a 0.5-L stirred-tank reactor with a turbine stirrer in a semibatch mode. Initial hydrogen uptake rates and dissolved hydrogen concentrations during this model reaction were measured as a function of the amount of catalyst in the liquid. The solubility of hydrogen in the pure liquid was determined by a gas absorption measurement at reaction conditions. From these measurements, the volumetric liquid-side mass transfer coefficient k L a at the gas−liquid interface was calculated as a function of catalyst loading. In addition, the k L a value was also determined in the absence of solid particles by the dynamic pressure drop method. Discrepancies that may result from calculating steady-state dissolved hydrogen concentrations using k L a values obtained from measurements conducted either in pure liquids or in liquids that contain suspended catalyst particles are discussed and illustrated by these measurements. The new method allows direct measurement of the concentrations of dissolved gases during a reaction, which can be a decisive factor for the rate as well as for the selectivity of a process. Estimations of the gas concentrations via reaction rate data and cumbersome determinations of k L a values are, therefore, no longer necessary.

Frau Professor Asima Chatterjee zum 60. Geburtstag gewidmet (7.1.78) Rwpolia hypercrateriformis M.R.: Isolation and Structure Elucidation of New Pyrrolidine Alkaloids SummaryThree new pyrrolidine alkaloids have been isolated from Ruspolia hypercrateriforrnis, which belongs to the plant family of Acanthaceae. The structure of the alkaloids ruspolinone (l), norruspoliiione (2) and norruspoline (3) (Scheme 1) has been elucidated by means of spectroscopic data of the pure compounds and their derivatives, by chemical transformation of 2 to 1 by methylation, by transformation of 3 and 2 to identical hydrogenation products, and by comparison of degradation products with synthetically prepared model compounds.