Acid Catalyzed Cyclization of Bis Silyl Diacylhydrazines: A New 1, 3, 4-Oxadiazole Synthesis

Diacylhydrazines are converted in good yields into 1,3,4-oxadiazoles with dichlorodimethyl-silane and trifluoromethane sulfonic acid.     

On the synthesis of 5‐ethyl meldrum's acid

Reductive alkylation of Meldrum's acid with acetaldehyde can give, depending on the experimental conditions, either a new dimer (5‐[3‐(2,2‐dimethyl‐4,6‐dioxo‐1,3‐dioxan‐5‐yl)butyl]‐2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione) or ethyl Meldrum's acid (2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione). A best way to obtain this latter product is synthesis of 1‐ethoxyethylidene Meldrum's acid from reaction of Meldrum's acid with triethyl orthoacetate, followed by a sodium borohydride reduction.     

Studies on pyrrolidones. Synthesis and reactivity of β-enaminomono-esters and β-enaminomononitriles derived from pyroglutamic acid

In the pyroglutamic acid series, β-enaminoesters 3 were formed in the 2-position by opening of the corresponding Meldrum's derivative 6 , and β-enaminonitriles 4 were obtained by treating carbamate vinylogous 5 by trimethytsilyl iodide. Alkylation and acylation of β-enaminoester 3a was briefly examined.     

Hydrogenic systems,frequency standards and fundamental constants

Hydrogenic (two-body) systems are the only atomic systems for which uncertainties in calculations of the energy levels approach the current state of the art in frequency measurement. This article discusses progress in the theory and measurement of transition frequencies in hydrogenic systems. These studies have relevance to the determination of fundamental constants and the testing of physical theories, especially quantum electrodynamics. A set of high accuracy calculable frequency standards could also be realized by using hydrogenic systems.     

Benzyl Derivatives of 3-Phenoxytoluene

3-phenoxybenzyl derivatives are of great interest in the chemistry of the pyrethroid insecticids since its chrysanthemate and isovalerate esters are the most active compounds against insects and the less toxic towards mammals.¹ However classical benzylic catalytic methods give poor yields in the case of the 3-phenoxytoluene, because of the deactivating effect of the 3-phenoxy substituent upon the benzylic hydrogen^2,3.     

Studies on pyrrolidinones: Some attempts to improve the synthesis of methyl n‐(3,4,4′,5‐tetramethoxybenzhydryl)pyroglutamate (hei 81) by using n‐acyl iminium salts methodologies

Some ways to use the N‐acyl iminium salt methodologies to synthesize a new inhibitor of tubulin polymerization, methyl N‐(3,4,4′,5‐tetramethoxybenzhydryl)pyroglutamate (HEI 81) were studied. The most interesting reactions utilize a new pyroglutamic lactone (3‐(3,4,5‐trimethoxyphenyl)dihydropy‐rrolo[1,2‐c]oxazole‐1,5‐dione).     

Studies on pyrrolidinones. Synthesis and reactivity of some n-protected pyroglutamic derivatives

The synthesis of pyroglutamoyl chloride N-protected by a methoxycarbonyl or a trifluoroacetyl group is described. Some aspects of the reactivity of these compounds and intermediates have been studied.     

New high-energy luminescence bands from Co2+ in ZnSe

Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co²⁺_Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed.     

Synthesis of 3′-deoxy-3′-C-methyl-β-d-ribonucleoside analogs

3′-Deoxy-3′-C-methyl-β-d-ribonucleoside analogs bearing the five canonical bases of nucleic acids have been synthesized. All these derivatives were prepared by glycosylation of the corresponding heterocyclic bases with a suitable peracylated 3-C-methyl sugar precursor. The synthesis of the 3-C-methyl sugar precursor is described following a new stereoselective synthetic pathway.     

Applications of 13C Nmr spectroscopy to structural assignment of derivatives of 2,3,4,5,6,7-hexahydro-1H-2-benzazonine

Treatment of 1,1-dimethyl-2-tolylpiperidinium halides with sodium amide in liquid ammonia affords derivatives of 2,3,4,5,6,7-hexahydro-1H-2-benzazonine via the Sommelet-Hauser rearrangement. Structures of the reaction products have been established by ¹³C nmr. In the case of 1,1-dimethyl-2-benzylpiperidinium halide, only an elimination reaction takes place.