Kálmán Újszászy

The ability of 2-phosphabicyclo[2.2.2]oct-5-ene 2-oxides to undergo fragmentation of the bridging P-moiety

Abstract New 2-phosphabicyclo[2.2.2]octene 2-oxides (2 and 3) were synthesized by the Diels–Alder reaction of 1,2-dihydrophosphinine oxides (1) and dienophiles, such as N-phenyl maleimide and maleic anhydride. The X-ray structure of one of the products (2Ab) suggests that the phosphabicyclooctenes have a less strained framework than the phosphabicyclooctadienes described earlier. As a consequence of this, also confirmed by thermal examinations and semiempirical calculations, thermal fragmentation of the phosphabicyclooctenes requires more forcing conditions, than that of the bicyclooctadienes. The methylenephosphine oxide (10) ejected could be utilized in the phosphorylation of hydroquinone in moderate yield. Mass spectral fragmentation of cycloadducts 2 and 3 under electron-impact conditions seems to be in agreement with the preparative experiences.

Preparation, crystal structure and thermal decomposition study of some trimethylsilyl esters of dicarbamic acids

Some new trimethylsilylated dicarbamic acid esters 1–9 and 10 were prepared. Their thermal decomposition was studied in n-alkanes as media. The reactions were monitored by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. Some N-silylated cyclic ureas 11–15 were also prepared from the corresponding esters 2–6 by thermolysis. The crystal structures of 2, 5 and 8 are also discussed. The crystal and molecular structures of 2 and 5 have very similar characteristics. Both molecules are sited via their molecular centre of symmetry on crystallographic inversion centres. The Carbamate groups are planar in all three cases as expected. An analysis of the data showed that the force due to SiO conjugation which constrains the Si atom into the plane of the carbamate group is comparable to the crystal packing forces with a small out-of-plane movement being not unfavourable.

Generation of p-dialkylamino methylenephosphine oxides by the photochemical fragmentation of 2-dialkylamino-2-phosphabicyclo[2. 2.2]- octa-5, 7-diene 2-oxides

Abstract A new P-amino phosphabicyclooctadiene is described which together with a similar derivative can be utilized in the generation of dialkylamino methylenephosphine oxides by photolysis. Reaction of these so far unknown intermediates with ethanol gives rise to N,N-dialkyl-O-ethyl methylphosphonamidates. The latter species were also formed by the photolysis of a P-ethoxy phosphabicyclooctadiene carried out in the presence of secondary amines.

New N-hydroxy carbamic acid trialkylsilyl derivatives: preparation and thermal reactions

Abstract New N-siloxy- or N-alkoxy-carbamic acid derivatives have been prepared. The crystal structure of N-siloxy-O-tert-butyl carbamate was determined. The thermal behaviour of these compounds was studied in the absence and in the presence of other reaction partners. The reaction products were identified by gas chromatography, gas chromatography-mass spectroscopy, IR spectroscopy and NMR. The experimental results can be explained by the formation of a radical-type transition state (carboxynitrene), detected by mass spectroscopy.

Preparation and solvolysis kinetics of trimethylsilyl N-alkyl-N-phenyl-carbamates

Abstract Some trimethylsilyl esters of N- phenyl -N- alkyl- (methyl-, ethyl -, n propyl -, i propyl -, n butyl -, t butyl -) carbamic acids were prepared by a novel method. Their solvolysis with isopropanol was studied. UV spectrophotometry was used to monitor the reaction and the pseudo first order rate constants were determined.A reaction mechanism is suggested on the basis of the dependence of rates on the ionic strength, on the temperature, on the isotope effect and on the concentration of various additives (sodium isopropoxide, sodium hydroxide, triethylamine and its hydrochloride, respectively).

New type of lariat ethers: Synthesis and cation binding ability of phosphonoalkyl-azacrown ethers

The synthesis of azacrown ethers with phosphonoalkyl side chains of two to five carbon atoms ( 3–8, 10), potentially useful as a new type of cation binding agent, is described. Introduction of the phosphonoalkyl moiety into the parent monoaza-15-crown-5 ( 1) decreases the cation extraction ability, but results in an increase in the selectivity towards the cations examined. The effect of the phosphonoalkyl-azacrown ethers on the properties of membranes used in ion-selective electrodes is also reported.

Synthesis of functionalized P-heterocycles including phosphine-borane complexes

Abstract Preparation of phosphinic chlorides, amides, and sulfide derivatives, as well as phosphine-borane complexes of P-heterocycles is described.

Alkyloximes and Imines via Silyl Carbamates

Abstract The reactions between different N,O-bis-trimethylsilyl-carbamates and oxo compounds were studied. The N,O-bis-trimethylsilyl-N-methoxy-carbamate converts ketones to the corresponding O-methyl oximes. The product is usually a mixture of syn and anti isomers. If the carbonyl compound bears a hydroxyl group, the oxime formation and the O-silylation take place simultaneously. In the case of α-haloketones, the undesired substitution of halogen was not observed. The reactions between N,O-bis-trimethylsilyl-N-methyl-carbamate and oxo compounds resulted in the corresponding imines, although the yield are moderate in some cases. Analoguos reaction of ferrocenylated oxo derivatives gave similar results.

Solvolysis kinetics of trimethylsilyl esters of aromatic N-carboxylic acids

Abstract Some new trimethylsilyl esters of cyclic and/or aromatic N -carboxylic acids were prepared. Their solvolysis reactions with isopropanol were studied by gas chromatography and by UV spectrophotometry respectively. The pseudo-first-order rate constants, the salt effects and the activation parameters were determined.

Synthesis of Phosphinines and its Saturated Devivatives:DI-, Tetra-and Hexahydrophosphinine Oxides

Abstract Our ring enlargement procedure1 is extended to the synthesis of valuable 1,2-dihydrophosphinie oxides (3), and 1,2,3,6-tetrahydrophosphininie oxides (4), with alkoxy substituent on the P-atom. Dichlorocarbene is added to the double bond of dihdro-]H-phosphole oxide 1 in the first step. The diastereoisomeric adducts (2 and 2∗) so obtained afford the ring expanded products (32 or 4) by the opening of the cyclopropane ring (Scheme I).