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Thomas Kaukorat

Bio: Thomas Kaukorat is an academic researcher from Braunschweig University of Technology. The author has contributed to research in topics: Intramolecular force & Substituent. The author has an hindex of 11, co-authored 57 publications receiving 348 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the role of the N, N ', N '-trimethylethylenediamine group as a substituent at phosphorus atoms in different coordination and/or oxidation numbers is discussed.

40 citations

Journal ArticleDOI
TL;DR: Although diverse phosphorus-containing heterocycles had been synthe-sized during the late nineteenth century already, work was still sparse in this area as recently as 1950[1,2] and the realization, around 1950, of the importance of phosphoruscontaining substances in biological processes resulted in intense activity in preparative organophosphorus chemistry, and in an upsurge of research on structural and mechanistic problems as discussed by the authors.
Abstract: Although diverse phosphorus-containing heterocycles had been synthe-sized during the late nineteenth century already, work was still sparse in this area as recently as 1950[1,2]. The realization, around 1950, of the importance of phosphorus-containing substances in biological processes resulted in intense activity in preparative organophosphorus chemistry, and in an upsurge of research on structural and mechanistic problems [3–6].

30 citations

Journal ArticleDOI
TL;DR: The reaction of 2-chloro-1,2-dihydro-1-methyl-4H-3,1-2-oxazaphosphorin-4-one and its 2-diethylamino-substituted derivative with various nucleophiles yielded novel and sometimes unexpected products.
Abstract: Reaction of some Dihydrobenzoxazaphosphorinones with Nucleophiles; Unusual Oxidation, Insertion, and Rearrangement Products and their Characterisation by Single-Crystal X-Ray Analysis The reaction of 2-chloro-1,2-dihydro-1-methyl-4H-3,1,2-oxazaphosphorin-4-one (2) and its 2-diethylamino-substituted derivative 3 with various nucleophiles yielded novel and sometimes unexpected products. Hydrolysis of 2 furnished the 2-hydroxybenzoxazaphosphorinone 4. In the presence of small amounts of water, two molecules of 4 were transformed into 5, accompanied by cleavage of one of the heterocyclic rings. The reaction of 2 with sodium chlorodifluoroacetate led, possibly in an Arbuzov-type reaction, to compound 6. The 1,5-diaza-4,8-cyclooctanedione system 7 was formed by reaction of 2 with 1,2,4,5-tetrakis(trimethylsilyloxy)benzene with concomitant loss of the phosphorus-containing group. 2,2′-Bis(trimethylsiloxy)biphenyl reacted with 2 in the expected fashion to form the diphosphorus compound 8. From 8 the chlorogold(I) complex 9 was obtained. The reaction of 3 with tetrachloro- and tetrabromo-o-benzoquinone did not lead to the expected spirocyclic products by oxidative addition of the quinone system to λ3P. Instead, cleavage and expansion of the heterocyclic ring system with formation of the tricyclic derivatives 10 and 11 took place. Compounds 5-10 were subjected to X-ray structure analysis. Compound 5 exists as two modifications 5a and 5b, which differ mainly in the relative orientation of the phenyl rings; intramolecular N–H…O hydrogen bonds are observed. Bond lengths at the halo-substituted carbon atom in 6 indicate steric crowding. The central 8-membered ring of 7 displays a “tub” conformation. Compound 8 undergoes a conformational change on complexation to the two gold(I) centres; one of the torsion angles C-O(exocyc.)-P-N is -163° in 8, but 95° in 9. The structure determination of 10 served only to confirm the (unexpected) connectivity; the crystal quality was too poor to allow quantitative conclusions.

24 citations

Journal ArticleDOI
TL;DR: New Phospholene and Phosphepine Derivatives from λ3-Phosphorus Compounds and Hexafluoroacetone or Perfluorinated α-Diketones.
Abstract: New Phospholene and Phosphepine Derivatives from λ3-Phosphorus Compounds and Hexafluoroacetone or Perfluorinated α-Diketones The reaction of the bis(2-chloroethyl)amino-substituted benzoxazaphosphorinone 1 with hexafluoroacetone (HFA) proceeds with insertion of the carbonyl group of HFA into the heterocycle of 1 to form the oxazaphosphepinedione 2. Triethyl phosphite (3) and triphenyl phosphite (4) react with the perfluorinated diketones 5 and 6 with formation of the pentaoxyphosphoranes 7–10 containing a dioxaphospholene ring system. The reaction of the (2-chloroethyl)amino- and bis(2-chloroethyl)amino-substituted 1,3,5,2-triazaphosphorinanediones 11–14 with the perfluorinated diketone C2F5C(:O)C(:O)CF3 (15) furnishes spirophosphorane derivatives with the dioxaphospholene ring system, 16 and 17, in two cases only. Compound 1 and 2-[bis(2-chloroethyl)-amino]-4H-1,3,2-benzodioxaphosphorin-4-one (18) react with the perfluorinated α-diketones 5 and 6 with insertion of the diketones into the heterocycle of 1 and 18 with formation of compounds 19–22 containing dioxa- and oxazaphosphepinone ring systems. The expected oxidative addition of the diketones to λ3P with formation of spirophosphoranes was not observed. Compounds 19–22 were obtained as mixtures of isomers (19a/b–22a/b). Single crystal X-ray structure analyses were conducted on 2 and 9. The seven-membered ring of 2 displays a “tub” conformation, with the O and benzo C atoms lying out of the plane of the other four atoms. The two independent molecules of 9 are similar, but differ in the degree of distortion from trigonal-bipyramidal geometry of phosphorus.

22 citations

Journal ArticleDOI
TL;DR: In this paper, the possibility of in tramolecular donor-acceptor-interaction between the nitrogen atom of the (CH3)2N group and the λ3P atom was investigated.
Abstract: The reaction of N,N′-dimethylanthranilic amide with phosphorus trichloride furnished 3, the first compound of P(III), involving the 1,3,2-benzodiazaphosphorinanone ring system. In the reaction of 3 with N-trimethylsilyl-N,N′,N′-trimethylethylenediamine 2 the product 4 was formed. The possibility of in tramolecular donor-acceptor-interaction between the nitrogen atom of the (CH3)2N group and the λ3P atom was investigated by 1H n.m.r. studies. No interaction was observed. Oxidative addition of elemental sulfur at the λ3P atom of 4 gave the λ4P-thiophosphoryl compound 5 while the reaction of 4 with methyl iodide and bromine, in an unusual reaction, furnished the ammonium salts 6 and 7. The N-Br bond in 7 was established by IR-spectroscopy. In the reaction of 4 with C7H8Cr(C0)4 (C7H″ = norbornadiene) a substitution product 8, involving intramolecular coordination of 4 to Cr(O) via λ3P and the nitrogen atom of the (CH3)2N grouping was formed. By contrast, the reaction of C7118Mo(CO)3 (C7H8 = cyclohept...

19 citations


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Book
01 Jan 1978

386 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the literature concerning the mechanism of the Kabachnik-Fields reaction and its significance for the chemistry of organophosphorus compounds as a method for the synthesis of α-amino phosphonates and their numerous functionally substituted derivatives and analogues, such as phosphinates and phosphine oxides, is presented.
Abstract: The published data of the last decade concerning the mechanism of the Kabachnik–Fields reaction and its significance for the chemistry of organophosphorus compounds as a method for the synthesis of α-amino phosphonates and their numerous functionally substituted derivatives and analogues, such as phosphinates and phosphine oxides, are generalised and systematised. The review discusses the classical version of the Kabachnik–Fields reaction, its modifications with the use of phosphorus chlorides, neutral esters and inorganic phosphorus acids, as well as chemical processes simulating separate steps of the reaction, viz., hydrophosphorylation of imines and amination of α-hydroxy phosphonates. Data on the practical application of α-amino phosphonates are presented. The bibliography includes 253 references.

223 citations

Journal ArticleDOI
TL;DR: A series of phosphine-diphenylphosphenium donor-acceptor cationic complexes have been synthesized and comprehensively characterized highlighting a versatile new synthetic method for P-P bond formation.
Abstract: A series of phosphine−diphenylphosphenium donor−acceptor cationic complexes have been synthesized and comprehensively characterized (phosphine = diphenylchlorophosphine, triphenylphosphine, trimethylphosphine, and tricyclohexylphosphine). The complexes involve homoatomic P−P coordinate bonds that are susceptible to ligand exchange reactions highlighting a versatile new synthetic method for P−P bond formation. Phosphenium complexes of 1,2-bis(diphenylphosphino)benzene and 1,2-bis(tert-butylphosphino)benzene undergo unusual rearrangements to give a “segregated” diphosphine−phosphonium cation and a cyclic di(phosphino)phosphonium cation, respectively. The rearrangement products reveal the kinetic stability of the phosphine−phosphenium bonding arrangement.

125 citations

Journal Article
TL;DR: In this article, the authors developed the theory of fixing the origin of the coordinate system in a polar space group by use of restraints (soft constraints or pseudoobservations) for any space group in any setting.
Abstract: The theory of fixing the origin of the coordinate system in a polar space group by use of restraints (soft constraints or pseudo-observations) is developed for any space group in any setting. The coefficients of the optimal restraint equation are on the average proportional to the square of the atomic numbers. They are determined directly from the unrestrained singular normal-equations matrix. Application of the restraint results in a positive-definite matrix which is as nearly diagonal as possible for the atomic positional coordinates along the origin-free axes. Correlations between these coordinates are therefore minimized. A very compact completely general and easily implemented algorithm results which functions without user intervention.

116 citations

Journal ArticleDOI
TL;DR: In spite of their electron-rich (lone pair bearing) nature, an extensive coordination chemistry is developing for Lewis acidic phosphines, which highlights a new synthetic methodology leading to new structure and bonding as discussed by the authors.
Abstract: Phosphines are traditional Lewis bases or ligands in transition metal complexes. In spite of their electron-rich (lone pair bearing) nature, an extensive coordination chemistry is developing for Lewis acidic phosphines, which highlights a new synthetic methodology leading to new structure and bonding.

97 citations