Jan Buter

CHEMICALLY MODIFIED FIELD-EFFECT TRANSISTORS - POTENTIOMETRIC AG+ SELECTIVITY OF PVC MEMBRANES BASED ON MACROCYCLIC THIOETHERS

A chemically modified field-effect transistor (CHEMFET) with satisfactory Ag+ selectivity is described. The potentiometric Ag+ selectivities of CHEMFETs with plasticized PVC membranes based on macrocyclic thioethers have been determined. All the macrocyclic thioethers tested showed silver response and a selectivity towards Ag + and Hg2+ versus other interfering cations. The highest Ag+ selectivity was obtained for a 14-membered cyclic tetrathioether with an exocyclic methylene group.

Improved Synthesis of C2-Symmetrical Pyridinediols and Synthesis of Cs-Symmetrical Pyridinediols

Base-induced reaction of 2,6-dimethylpyridine (2,6-lutidine) (1) with two equivalents of various ketones has been reported to provide C-2-symmetrical pyridine diols 3. Closer examination reveals that competitive di-addition to a single methyl group can occur providing C-s-symmetrical pyridine diols 7. By varying the lithiation times, the formation of this side product could be maximized or minimized on the basis of a mechanistic proposal for the competing pathways. The formation of the C-s-diol 7 could be excluded completely by using potassium diisopropylamide as base; high yields of C-2-symmetrical pyridine diols 3 are obtained. Regioselective additions of 1 to (R)-fenchone and (-)-menthone were also achieved.

SYNTHESIS OF THE MACROCYCLIC THIOCROWN ETHERS 1,4,7,10,13,16,19-HEPTATHIAHENEICOSANE (21-S-7) AND 1,4,7,10,13,16,19,22-OCTATHIATETRAEICOSANE (24-S-8)

Abstract The synthesis and characterization of the two macrocyclic sulfides, 1,4,7,10,13,16,19-heptathiaheneicosane (21-S-7) and 1,4,7,10,13,16,19,22-octathiatetraeicosane (24-S-8), are described starting from different combinations of dithiols and dichlorides of differing chain lengths. Cs2CO3, is used for the cyclizations.

Synthesis of mesocyclic and macrocyclic thiacrown ethers containing -SCH2SCH2S- units using thio(bischloromethane)

Abstract Oxidative cleavage of 1,3,5-trithiane 1 by the thionyl chloride is promoted by a catalytic quantity of a Lewis acid like zinc bromide or aluminum chloride and results in the formation of pure thiobis (chloromethane) ( 2 ). This reagent has been successfully employed in the straightforward synthesis of a novel series of thiacrown ethers possessing methylene bridges between the heteroatoms. These molecules have chemical and physical properties that differ considerably in their solubilities from those of their ethylenic or propylenic counterparts.

Sulfonyl-1,3-dicarbanions. Evidence concerning the scope and limitation of formation. Oxidation with copper salts to form alkenes.

Aus den Sulfonen (I) werden mit uberschussigem Butyllithium oder durch eine stufenweise Reaktion mit Diisopropyllithium und Butyllithium die Dianionen (II) erhalten, die z.B. zu (III) methyliert oder auch bei der Behandlung mit Oxidationsmitteln uber (IV) zu den Olefinen (V) oxidiert werden konnen.

Synthesis, complexation behaviour and reactions of thia-crown ethers incorporating propan-2-one units

Thia-crown ethers containing ketone functionality derived from 1,3-dichloroacetone have been prepared in 70–80% yields; the crystal structures of one free macrocycle and two AgI complexes have been determined.

Functionalization of thiocrown ethers containing the thioacetal unit

Abstract Thiocrown ethers containing thioacetal units are readily prepared by reaction of the cesium salts of long chain dithiols with methylene dibromide. Preparation of the trimethylsilyl derivatives followed by condensation with aldehydes under basic conditions (Peterson reaction) leads to the expected macrocycles with exocyclic double bonds at the thioacetal carbon atom.

Boric acid mediated preparation of mesocyclic thiocrown ethers containing xylylene units. Molecular structures of 3,8-dibenzo-1,6-di-thiacyclodecane and 2,5,8-trithia-(9)-p-benzenophane

Reaction of a dithiol with B(OH)3 and base in MeOH followed by reaction with xylylene dibromides proceeds selectively to give the corresponding ortho, meta or para-cyclophanes in good yield (70-86 %). The syntheses of examples of all three types of benzenophanes are discussed. The molecular structures of 3,8-dibenzo-1,6-dithiacyclodecane (8) and 2,5,8-trithia-(9)-p-benzenophane (5) have been determined by X-ray crystallography. Crystal data for 8: space group P2(1)/c with a=8.2745(10), b=4.9330(10), c=16.5500(12) A, beta=100.37 (1)-degrees, Z=2; R=0.043 (R(w)=0.045) for 949 reflections (I>2.5 sigma (I)). Crystal data for 5 (150K): Space group P2(1)/c with a=10.310(1), b=7.430 (1), c=17.681(2) A, beta=113.27(1)-degrees, Z=4; R=0.065 (R(w)=0.065) for 1969 reflections (I>2.5 sigma(I)).

Functionalized thia-crown ethers. Synthesis, structure, and properties

A caesium promoted synthesis of this-crown ethers containing isobutenyl units in the periphery is described, including structural data and a method involving diborane for functionalization of the methylene group.

Rapid Preparation of Raney Nickel Catalysts Demineralization with Ion-Exchange Resin

Abstract The usual preparation of raney nickel catalysts W-21), W-5, and W-62)involves a tedious and time-consuming wasning process with distilled water to remove the last traces of salts. we found that this demineralication can more conveniently be accomplished with ion-exchange resin. The procedures described below have been inuse for several years a our laboratory, where large quantities of Raney Nickel are needed for desulfurization and hydrogenation experiments.