Synthesis of C-(N,N-dialkylamino)phosphaalkenes

New C-(N,N-dialkylamino)phosphaalkenes were synthesized by the reaction of phenylphosphine with amidacetals. Such compounds may also be synthesized by the reaction of bis(trimethylsilyl)phenylphosphine with amidacetals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1639–1641, July, 1990.     

Bis-(N2-hydroxyhexafluoroisopropyl-N1,N1-substituted)terephthalamidines and their reaction with perfluorohexanecarbonitrile

Bis(N²-hydroxyhexafluoroisopropyl-N¹,N¹-substituted) terephthalamidines, which are stable up to their melting points, were obtained by reacting substituted tetraphthalamidines with hexafluoroacetone. The reaction of bis(N²-hydroxyhexafluoroisopropyl-N¹N¹-substituted)terephthalamidines with perfluorohexanecarbonitrile results in the formation of 1,4-bis(2,4-per-fluorohexyltriazinyl) benzene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1613–1616, July, 1990.     

Synthesis and structural characterization of sulfur rich iron (II) carbonyl dimers: Facile reversible reaction with carbon monoxide

The sulfur-rich iron carbonyl dimer complexes [Fe(CO)₂(S′^SiS₂)]₂ (2), and [Fe(CO)(S′^SiS₂)]₂ (3) have been prepared. The [2Fe-2S] cores of the new complexes are planar. The binding mode of the tridentate sulfur ligand in complex 2 is facial with a S(thiolate)-Fe-S(thiolate) angle of 92°, while in complex 3, the S′^SiS₂ ligand binds the metal with a S(thiolate)-M-S(thiolate) angle of 120°. The Fe-Fe distance is reduced from 3.45 Å in complex 2 to 2.78 Å in the 32 electron dimer complex 3. Complexes 2 and 3 are at equilibrium in solution and can be readily interconverted by addition or removal of CO.     

Reaction of phenylsulfenyl chloride with C-(N,N-dimethylamino)-methylene-P-phenylphosphine

PhSCl adds regiospecifically to the P=C double bond in C-(N,N-dimethylamino)-methylene-P-phenylphosphine to give PhP(SPh)₂ and Cl₂CHNMe₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 948–949, April, 1991.     

Triarylimidazole radicals and their dimers (review)

Despite the fact that 2,4,5-triarylimidazoles have long been known [1] and have always been attractive to investigators as subjects for the study of chemiluminescence, it was only in 1960 that it was found that stable free radicals are formed during their oxidation and that the radicals form dimers in the crystalline state that have piezo-, photo-, and thermochromic properties. The aim of the present review is a correlation of the known information on the chemistry of stable radicals of the triarylimidazolyl series.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1387–1390, October, 1972.     

Evidence of reversibility in azo-coupling reactions between 1,3,5-tris(N,N-dialkylamino)benzenes and arenediazonium salts

The reactions between strongly electron-rich aromatic substrates (1,3,5-tris(N,N-dialkylamino)benzenes, neutral carbon super nucleophiles) and diazonium salts produce moderately stable sigma complexes (Wheland complexes). The reactivity of Wheland complexes with electrophiles (other diazonium salts, or 4,7-dinitrobenzofuroxan) produces exchange reactions in the electrophilic part: the better electrophile replaces the less powerful electrophile. In the same way, in Wheland complexes with the 1,3,5-tris(morpholinyl)benzene, the 1,3,5-tris(piperidinyl)benzene replaces the less powerful nucleophile 1,3,5-tris(morpholinyl)benzene. Evidence is reported here indicating that for the title system the reaction of the attack of the electrophilic reagent producing Wheland complexes is a reversible process. The final products of the diazo-coupling reactions undergo a further attack of some diazonium salts. From the final products of the double diazo-coupling reactions (diazo compounds), we collected evidence that is a clear instance of complete reversibility of the diazo-coupling reaction.     

The reaction of chloroalkyl(vinyl)silanes with N,N-dichloro sulfonamides

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S(N)2 reaction of sulfur nucleophiles with hindered sulfamidates: enantioselective synthesis of alpha-methylisocysteine

The work described here demonstrates that the five-membered cyclic alpha-methylisoserine-derived sulfamidate, (R)-1, behaves as an excellent chiral building block for the ring-opening reaction by S(N)2 attack with sulfur nucleophiles at the quaternary carbon. As a synthetic application of this methodology, and to show that this sulfamidate is a valuable starting material, the synthesis of two new alpha-methylisocysteine derivatives has been carried out to cover the lack of alpha- and beta-methylated amino acids that incorporate the cysteine or isocysteine skeleton. These compounds are two new alpha,alpha-disubstituted beta-amino acids (beta(2,2)-amino acids), and the synthetic routes involve nucleophilic ring opening followed by acid hydrolysis.     

Remarkable diastereoselectivity in the addition of allylic and unsaturated diorganozinc reagents to beta-(N,N-dialkylamino)-aldehydes

1,3-Anti amino alcohols 5(a)-18(a) are obtained with high diastereoselectivity by use of diorganozinc reagents in additions to amino aldehydes 2a and 2b. The corresponding Grignard reagents exhibit low to modest diastereoselectivity. The highly diastereoselective zinc-based method makes available a wide range of 4,4-disubstituted cyclohexenone derivatives containing contiguous stereocenters.     

杂芳核对(N-N-二烃基胺基)二氯硼烷的三烃基化反应, 二乙胺合三(2-苯并噻唑基)硼烷的合成及其晶体结构

本文报道(N,N-二烃基胺基)二氯硼烷的反常三烃化反应, 2-苯并噻唑基Grignard剂与(N,N-二乙胺基)二氯硼烷反应, 得到二乙胺合三(2-苯并噻唑基)硼烷, 并讨论了反应机理。分子结构经X单晶结构分析确证。晶体结构属正交晶系, 空间群为P212121, 晶胞参数a=11.570(3), b=12.496(4), c=16.577(4)nm; Z=4, V=2397.3nm^3,Dc=1.348g/cm^3, μ(MoKa)=3.167cm^-^1。     

Kinetics and mechanism of reaction of trans-(diaqua)(N,N′-ethylene-bis-salicylidenimine) chromium(iii) with sulfur(iv): The labilizing effect of coordinated sulfite

The reaction of trans-[Cr(Salen)(OH₂)₂]⁺ with aqueous sulfite yields trans-[Cr(Salen)(OH₂)(OSO₂(SINGLEBOND)O)]⁻ (O-bonded isomer). The rate and activation parameter data for the formation of the sulfito complex are consistent with a mechanism involving rate-limiting addition of SO₂ to the Cr^III(SINGLEBOND)OH bond. The complex ions, trans-[(OH₂)Cr(Salen)(OSO₂(SINGLEBOND)O)]⁻, and trans-[(OH)Cr(Salen)(OSO₂(SINGLEBOND)O)]²⁻, undergo reversible anation by NCS⁻, N₃⁻, imidazole, and pyridine resulting in the formation of trans-[XCr(Salen)(OSO₂(SINGLEBOND)O)]^(N+1)−(n=1 for X=N₃⁻,NCS⁻, and 0 for X=imidazole and pyridine) predominantly via dissociative interchange mechanism. The labilizing action of the coordinated sulfite on the trans-Cr^III-X bond in trans-[XCr(Salen)(OSO₂)]⁽ⁿ⁺¹⁾⁻ follows the sequence: NCS⁻pyridine ca. N₃⁻ ca. imidazole. Data analysis indicated that the coordinated sulfite has little trans activating influence. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 373–384, 1998     

Chemical shifts in the29Si NMR spectra and intramolecular reaction mechanisms in C,C-bis(trimethylsilyl)phosphaalkenes

The changes in the chemical shifts of³¹P,¹³C, and²⁹Si nuclei in structurally similar phosphaalkenes of the series XⁱP = C(SiMe₃)₂ have been investigated. The specific influence of the electrons of each of the four groups of substituents Xⁱ on the delocalized -system –P = C(Si^E, Si^Z) has been revealed. When the effect of conjugation (or hyperconjugation) from Xⁱ is strengthened, the screening of the Si^Z atom increases as the Si^E atom loses its screening. In the case of Xⁱ with a predominant inductive effect (halogens, uncojugated groupings) the changes in the screening of Si^Z and Si^E are symbatic. The correlations of the chemical shifts _a with Hammett's -constants and the behavior of the ionization potentials of the -and n_p energy levels in these compounds are discussed. It is assumed that the asymmetry in the degree of screening of the Si^E and Si^Z atoms is related to the participation of the unshared electron air of the P atom in the reaction with the –C(SiMe₃)₂ groupings.Institute of Organic Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 703–710, November–December, 1991. Original article submitted May 21, 1990.     

The reaction of Mn and Re carbonyls with some bis(N,N-dialkylselenocarbomoyl) selenides

Several complexes of the types I = [M(CO)₄L], II = [M(CO)₃L]₂ and III = [Re(CO)(Et₂dsc)₃](M = Mn, Re; L = Et₂dsc; modsc) are prepared by reaction of M₂(CO)₁₀ with L-L: a 1:1 mixture of R₂NC(Se)Se(Se)CNR₂ and R₂NC(Se)Se₃(Se)CNR₂ (R = Ethyl or R₂ = Morpholyl). On the basis of IR and molecular weights, all the compounds prove to have the diselenocarbamate group acting as bidentate. Compounds I are monomeric and six-coordinate; compounds II are dimeric with a proposed selenium bridging structure and compound III is suggested as seven-coordinate. The resemblance between S and Se atoms in analogous compounds is once more pointed out.     

Stereoselective synthesis of cationic heterobidentate C(NHC)/SR rhodium(I) complexes using stereodirecting N,N-dialkylamino groups

The synthesis of two different types of chiral C/S ligands based upon N-(N,N-dialkylamino)-substituted N-heterocyclic carbenes and thioether functionalities, along with their neutral [RhCl(CNH)(COD)] and cationic [Rh(I)(NHC/S)(COD)]⁺ complexes, has been accomplished. (S)-2-[(Phenylthio)methyl]pyrrolidine, carrying the thioether moiety, and (2S,5S)-2,5-diphenylpyrrolidine, combined with a thioether functionalized side chain, were studied as potential stereodirecting groups. Only the latter provided high selectivity in the formation of the neutral complex, leading to a single atropoisomer (de >98%) of the newly formed, configurationally stable C(NHC)–Rh bond. The synthesis of the corresponding cationic [Rh(I)(NHC/S)(COD)]⁺ complexes, however, resulted in the formation of single (R_a,S_S) and (S_a,S_S) diastereomers, respectively, of the four possible complexes in each case [combinations of the (R_a/S_a) C(NHC)–Rh axis and the (S_s/R_s) stereogenic S center formed upon coordination]. For the proline derivative, the resolution of the mixture of (R_a/S_a)-[RhCl(CNH)(COD)] neutral complexes proceeds via dynamic kinetic resolution through coordinatively unsaturated Rh(I) intermediates formed after halide abstraction. The absolute configurations of both types of cationic complexes were unequivocally assigned on the basis of X-ray diffraction analysis.     

trans-Dichloro(triphenylarsino)(N,N-dialkylamino)platinum(II) Complexes: In Search of New Scaffolds to Circumvent Cisplatin Resistance

The high incidence of the resistance phenomenon represents one of the most important limitations to the clinical usefulness of cisplatin as an anticancer drug. Notwithstanding the considerable efforts to solve this problem, the circumvention of cisplatin resistance remains a challenge in the treatment of cancer. In this work, the synthesis and characterization of two trans-dichloro(triphenylarsino)(N,N-dialkylamino)platinum(II) complexes (1 and 2) were described. The trypan blue exclusion assay demonstrated an interesting antiproliferative effect for complex 1 in ovarian carcinoma-resistant cells, A2780cis. Quantitative analysis performed by ICP-AES demonstrated a scarce ability to platinate DNA, and a significant intracellular accumulation. The investigation of the mechanism of action highlighted the ability of 1 to inhibit the relaxation of supercoiled plasmid DNA mediated by topoisomerase II and to stabilize the cleavable complex. Cytofluorimetric analyses indicated the activation of the apoptotic pathway and the mitochondrial membrane depolarization. Therefore, topoisomerase II and mitochondria could represent possible intracellular targets. The biological properties of 1 and 2 were compared to those of the related trans-dichloro(triphenylphosphino)(N,N-dialkylamino)platinum(II) complexes in order to draw structure–activity relationships useful to face the resistance phenotype.     

1,3-Bis(N,N-dialkylamino)imidazolin-2-ylidenes: synthesis and reactivity of a new family of stable N-heterocyclic carbenes

The synthesis of stable 1,3-bis(N,N-dialkylamino)imidazolin-2-ylidenes was accomplished from readily available chiral bis-hydrazones after reduction or addition of PhMgCl, cyclization to imidazolinium salts, and treatment with KN(SiMe3)2. This strategy allows the obtention of free imidazolin-2-ylidenes and their Rh(COD)Cl complexes in enantiomerically pure form. The sigma-donor ability of dialkylamino-substituted diaminocarbenes was found to be slightly higher than that of alkyl(aryl) analogues.     

The reaction of sulfur with organic compounds

The most effective catalyst for thionation of cumenes to 4-aryl-1, 2-dithiol-3-thiones, have been proven to be sym-diphenylguanidine, mercury acetamide, mercaptobenzthiazole + ZnO. The way in which thionation of cumeme derivatives depends on the nature of the substituent in the aromatic ring is investigated. Eight derivatives (4 previously unknown) of 4-phenyl-1, 2-dithiol-3-thione, with a chlorine atom and an alkyl or alkoxy group in the benzene ring are synthesized and described.For previous papers see [1–6].