Photoinduced addition and addition–elimination reactions of perfluoroalkyl iodides to electron-deficient olefins

Photoinduced radical perfluoroalkylation of various simple electron-deficient olefins was achieved in the presence of an aqueous Na₂S₂O₃ solution. The reactions proceeded smoothly to give addition or addition–elimination products. The ability of the products to be used as radical precursors or Michael acceptors was also demonstrated.     

Synthesis of the p-keto acids from benzimidazolium iodides and ethyl malonate

The reaction of benzhnidazole methiodide with ethyl malonate in the existence of base was studied,and a new convenient synthetic method of the β-keto acid was provided.     

Studies on polyhaloalkanes Ⅰ.Radical addition of polyfluoroalkyl iodides to diethyl allylphosphonate

Radical addition of polyfluoroalkyl iodides to the C=C double bond of diethyl allylphos-phonate was carried out in CH_2Cl_2-H_2O two-phase medium in the presence of sodium dithioniteto give dicthyl 3-polyfluoroalkyl-2-iodopropylphosphonates(3)in excellent yields.Compounds 3were then converted to diethyl polyfluoroalkanephosphonates(4)by zinc-reduction,Thus a facilemethod for preparing polyfluoroalkanephosphonates is realized.     

ESR studies on the reactions of the sulphite radical anion,SO−3, with olefinic compounds in aqueous solutions

The reactions of the sulphite radical anion, SO⁻₃, which was generated either from a Ce⁴⁺-NaHSO₃ system at pH 2.5 or from a Ti³⁺ (ethylenediaminetetraacetic acid)-H₂O₂-Na₂SO₃ system at pH 9 in aqueous solutions, with some olefinic compounds were investigated by use of a rapid-mixing flow technique coupled with ESR which can detect the radicals having a lifetime of 5-100 ms. The SO⁻₃ radical could add to the CO double bond in the olefinic compounds in both acidic and alkaline aqueous solutions, although the SO⁻₃ radical is more active in acidic conditions than in alkaline conditions. From the observed hyperfine splitting constants of the SO⁻₃ adducts of the olefinic compounds, the preferred conformation of the adducts was discussed.     

Studies on selective β/β′ bromination of π-extended porphyrins and subsequent coupling reactions

Monobromination of β, β′-π-extended porphyrins was found to selectively occur at the β or β′ position of the porphyrins which is antipodal to the fused aromatic ring. Subsequent Sonogashira or Heck coupling of the resultant bromoporphyrin introduced a carboxylphenylethynyl group or an acrylic acid group to the π-extended porphyrin. The optimal reaction conditions were found for the Sonogashira and Heck coupling reaction. All of the coupling products have shown a broadening and red-shift of the Soret band and Q bands in the UV–Vis absorption spectra compared with the π-extended porphyrin starting materials and the original unmodified porphyrins.     

Studies on sulfinatodehalogenation:The reaction of polyfluoroalkyl iodides and bromides with sodium bisulfite

Without oxidant, sodium bisulfite reacted with polyfluoroalkyl iodides and bromides in aqueous DMF solution to give the corresponding sulfinates in good yields.     

Homogeneous multimetallic catalysts: Part 10. Formylation of aryl and alkenyl iodides by palladium—ruthenium bimetallic catalysts

The PdCl₂(PPh₃)₂—Ru₃(CO)₁₂ bimetallic system exhibited higher catalytic activity for the formylation of aryl and alkenyl iodides than PdCl₂(PPh₃)₂ or Ru₃(CO)₁₂ alone. Thus, in the formylation of iodobenzene (at 70 °C for 1.5 h under 50:50 atm of CO:H₂), the yield of benzaldehyde by PdCl₂(PPh₃)₂—Ru₃(CO)₁₂ catalyst (Pd:Ru = 1:2) was about four times as high as that by PdCl₂(PPh₃)₂ alone. Carbonyl complexes of other metals, such as Mn₂(CO)₁₀, Co₂(CO)₈, Cr(CO)₆, Fe(CO)₅, Mo(CO)₆ and W(CO)₆ were ineffective as the second component of the catalyst. To clarify the mechanism of the synergistic effects, the reaction of PdI(CO-p-Tol)(PPh₃)₂ with [HRu₃(CO)₁₁]⁻ or [HRu(CO)₄]⁻, ruthenium hydride species known to be generated under the catalytic formylation conditions, was performed. The reaction rapidly proceeded at 40 °C by dinuclear reductive elimination to form p-tolualdehyde, although the reaction with molecular hydrogen was very slow. These results strongly suggest that the improved catalytic activity of the Pd—Ru system is attributable to the high hydrogenolysis activity of in-situ-generated ruthenium hydride species.     

Studies on the asymmetric synthesis of huperzine A. Part 2: Highly enantioselective palladium-catalyzed bicycloannulation of the β-keto-ester using new chiral ferrocenylphosphine ligands

New chiral ferrocenylphosphine ligands were designed and tested in the enantioselective bicycloannulation of β-keto-ester 2 with bifunctional allylic agent 4. A range of e.e. values from 80 to 90% of the bicyclic intermediate 6 was achieved. Subsequently, enantiopure (−)-huperzine A was prepared in ca. 40% yield from β-keto-ester 2.     

Studies on sulfinatodehalogenation ⅩⅩⅧ.The addition of polyfluoroalkyl iodides to olefins initiated by sodium disulfite

Polyfluoroalkyl iodides reacted with olefins in aqueous DMF solution of sodiumdisulfite under mild conditions to give the corresponding 1:1 adducts in good yields,providinga convenient polyfluoroalkylation method.This indicated that R_F radicals were formed inthe reaction of polyfluoroalkyl iodides and sodium disulfite.A SET mechanism is proposedfor the sulfinatodehalogenation reaction of sodium disulfite.     

Experimental and Theoretical Studies on the Inclusion Complexation of β-Cyclodextrin with Phenothiazine Derivatives

Inclusion complexation of -cyclodextrin (-CD) with N-phenylphenothiazine ( 1), N-benzylphenothiazine ( 2) and N-phenethylphenothiazine ( 3) has been studied by means of UV-vis spectroscopy and molecular dynamics simulations. The association constants (K_a) were determined to be 126, 312 and 211 dm³/mol for inclusion of -CD with 1, 2 and 3, respectively. It shows that the K_a values are affected by the substituents of the guest compounds. The structures of the complexes and the conformation of the guest compounds bound by -CD in the complex have been discussed.     

Studies on adducts of tin tetrahalides and titanium tetrachloride with β-aminothiones and β-ketoamines

The solid state configurations of 1 : 1 and 1: 2 adducts formed by tin tetrahalides and titanium tetrachloride with β-aminothione, CH₃ C(S)CHC(NHCH₃)CH₃, (MeSN MeMe), tetradentate amino-thione, H₂[(sacac)₂en] and β-ketoamines R¹C(O)CHC(NHR)R², (R¹ONRR ²) have been investigated. The i.r. spectra of the addition compounds suggested that the bi- and tetradentate aminothiones coordinated tin(IV) and titanium(IV) through the nitrogen atom and the β-ketoamines through the oxygen. The conducting behaviour of the products of tin tetrahalides in non-aqueous solvents of high dielectric constant exhibits some interesting trends with the change of the halide group.     

Influence of the size and geometry of the anion binding pocket of sugar–urea anion receptors on chiral recognition

Three new chiral urea-type anion receptors were synthesized from aromatic diamines and 1-amino-1-deoxyglucose. The anion binding properties of these receptors were studied using chiral carboxylates derived from mandelic acid and three α-amino acids. We found that the size of the anion binding pocket played an important role in chiral recognition processes. The best results were obtained for 1,8-diaminoanthracene and α-amino acid anions.     

Studies on the Syntheses of the Side Chains of Brassinolide and Dolicholide

(4R,5S)-2,2-Dimethyl-4-(1',2'-dimethylpropyl)-5-(1'-bromoethyl)--1,3-dioxolane(15) with the side chain of brassinolide and (4R, 5S)--2, 2-dimethyl-4-(l'-methylene-2'-methylpropyl)-5-(1'-bromoethyl) 1,3-dioxolane(14) with the side chain of dolicholide were first synthesized through 11 and 10 stepes from D-mannitol respectively. All of the intermediates 7-13 were first synthesized too.     

Studies on the Protonation and Complexations of Dioxotetraamine Macrocycles

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Oxidation of phenol in aqueous acid: characterization and reactions of radical cations vis-à-vis the phenoxyl radical

Aqueous sulfuric acid containing up to approximately 14 M acid (H0 > or = -7.0) was used as solvent in pulse radiolytic redox studies to characterize cationic transients of phenol (C6H5OH) and map their reactions. The primary radical yields were first measured to correlate the variation in various radical concentrations as a function of increasing acid fraction in the solvent. Compared to their respective values at pH 2, the G(Ox*) increased with almost a linear slope of approximately 0.024 micromol J(-1) for H0(-1) (or pH(-1)) up to H0 -6.0 (Ox* = *OH + SO4*-), whereas G(H*) increased with a slope of approximately 0.033 micromol J(-1) for H0(-1) (or pH(-1)) up to H0 -5.0. In the presence of > 10 M acid (H0 < -5.0), phenol was oxidized to its radical cation, C6H5OH*+, which further reacted with phenol and generated the secondary, dimeric radical cation, (C6H5OH)2*+, following an equilibrium reaction C6H5OH*+ + C6H5OH <==> (C6H5OH)2*+, with K(eq) = 315 +/- 15 M(-1). The two cationic radicals were characterized from their individual UV-vis absorption spectra and acidity. The C6H5OH*+ absorption peaks are centered at 276 and 419 nm, and it was found to be more acidic (pKa = -2.75 +/- 0.05) than (C6H5OH)2*+ (pKa = -1.98 +/- 0.02), having its major peak at 410 nm. On the other hand, in the presence of < 6.5 M acid the C6H5O* reactions followed the radical dimerization route, independent of the parent phenol concentration.     

Studies of the ligand effect on the synthesis of dialuminoxanes by various β-diketiminato ligands

Reactions of LH (L = HC[C(Me)N(2,6-Me(2)C(6)H(3))](2)) with Me(n)AlCl(3-n) in diethyl ether afforded the adducts LH·AlMe(n)(Cl)(3-n) (n = 2, 3; 1, 4; 0, 5) in good yields. Treatment of 3 at elevated temperatures in toluene resulted in LAlMeCl (2) by intramolecular elimination of methane. The controlled hydrolysis of LAlMeCl (2) with equimolar amounts of water in the presence of N-heterocyclic carbene (NHC) gave a mixture of [LAl(Me)](2)(μ-O) (7) and dimeric [LAlMe(μ-OH)](2) (8). A convenient route for the preparation of [LAlMe(μ-OH)](2) (8) was the NHC-assisted controlled hydrolysis of LAlMeI (9). Stepwise hydrolysis of LAlH(2) (11) gave dialuminoxane hydride [LAl(H)](2)(μ-O) (12) and dialuminoxane hydroxide [LAl(OH)](2)(μ-O) (13), respectively. Anhydrous treatment of LAlCl(2) (1) or LAlMeCl (2) with Ag(2)O afforded chlorinated dialuminoxane [LAl(Cl)](2)(μ-O) (14) and [LAl(Me)](2)(μ-O) (7), respectively.     

Studies on the formation and properties of polypyrrole doped with ionised β-cyclodextrins: influence of the anionic pendants

Journal of Solid State Electrochemistry - Polypyrrole films doped with sulfonated β-cyclodextrin (PPy/sβ-CD) and carboxymethyl β-cyclodextrin (PPy/CMβ-CD) were formed on...     

Diversity-oriented synthesis based on the DPPP-catalyzed mixed double-Michael reactions of electron-deficient acetylenes and β-amino alcohols

In this study, we prepared oxizolidines through 1,3-bis(diphenylphosphino)-propane (DPPP)-catalyzed mixed double-Michael reactions of β-amino alcohols with electron-deficient acetylenes. These reactions are very suitable for the diversity-oriented parallel syntheses of oxizolidines because: (i) they are performed under mild metal-free conditions and (ii) the products are isolated without complicated work-up. To demonstrate the applicability of mixed double-Michael reactions for the preparation of five-membered-ring heterocycles, we prepared 60 distinct oxazolidines from five β-amino alcohols and 12 electron-deficient acetylenes. We synthesized 36 of these 60 oxazolidines in enantiomerically pure form from proteinogenic amino acid-derived β-amino alcohols.