Quinazolines and 1,4-benzodiazepines. XLVI. Photochemistry of nitrones and oxaziridines

The cyclic nitrones 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide ( 5a ) and 1,3-dihydro-7-methylthio-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide ( 5b ) are photoisomerized to readily isolable oxaziridines, 7-chloro-4,5-epoxy-5-phenyl-1,3,4–5-tetrahydro-2H-1,4-benzodiazepin-2-one ( 6a ) and 4,5-epoxy-5-phenyl-1,3,4,5-tetrahydro-7-methylthio-2H-1,4-benzo-diazepin-2-one ( 6b ). Oxaziridine 6b upon further irradiation gave ring expansion and ring contraction products, 4,6-dihydro-2-phenyl-9-methylthio-5H-1,3,6-benzoxadiazocin-5-one ( 7b ) and 4-benzoyl-3,4-dihydro-6-methylthioquinoxalin-2(1H)-one ( 8b ) respectively. The ring contraction product, 4-benzoyl-6-chloro-3,4-dihydroquinoxalin-2(1H)-one ( 8a ), was obtained from irradiation of oxaziridine 6a .     

Manganese(II) and copper(II) hexafluoroacetylacetonate 1:1 complexes with 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine: regiochemical parity analysis for exchange behavior of complexes between radicals and paramagnetic cations

Mn(hfac)(2) and Cu(hfac)(2) form coordination complexes with 5-(4-[N-tert-butyl-N-aminoxyl]phenyl)pyrimidine, PyrimPh-NIT. (Mn[PyrimPh-NIT](hfac)(2))(2) and (Cu[PyrimPh-NIT](hfac)(2))(2), 1 and 2, respectively, are cyclic M(2)L(2) dimers that exhibit strong exchange coupling between the coordinated paramagnetic dication (M) and nitroxide (NIT) unit. The M-NIT exchange is strongly antiferromagnetic (AFM) in 1 and strongly ferromagnetic (FM) in 2. Magnetic susceptibility measurements for 1 were fitted to an AFM spin pairing model with J/k = -0.25 K between Mn-NIT spin sites units. Complex 2 also exhibits AFM spin pairing between S = 1 Cu-NIT spin units that is somewhat field dependent at low temperature. The fit of corrected paramagnetic susceptibility chi(T) to an AFM spin pairing model at 200 Oe yields J/k = (-)3.8 K, quite similar to earlier measurements at 1000 Oe yielding J/k = (-)5.0 K. At 1.40 K, the magnetization of 2 does not approach saturation until somewhat above 170 kOe, giving an S-shaped curve; at 0.55 K, the magnetization curve shows steps characteristic of field-induced crossover between the S = 0 ground state and excited spin states. From the steps in the 0.55 K data, we estimate J/k = (-)3.8-4.0 K for 2, in good agreement with the analysis of chi(T).     

Optical-optical double-resonance spectroscopy of BaO: The low-lying states

Optical-optical double-resonance (OODR) induced photoluminescence into the lowest excited electronic states of BaO—a³Σ⁺, A¹Σ⁺, b³Π, and $\text{A′}{}^1\text{Π}$—from C¹Σ⁺ is described. These low-lying states are deperturbed to obtain spectroscopic constants and potential energy curves:

     

24.

Hybrid microgels photoresponsive in the near-infrared spectral range   总被引：4，自引：0，他引：4  

Gorelikov I  Field LM  Kumacheva E 《Journal of the American Chemical Society》2004,126(49):15938-15939

We report for the first time a photothermally responsive composite material based on polymer microgel particles doped with gold nanorods. We used the dependence of the longitudinal surface plasmon of the gold nanorods on their aspect ratio to synthesize nanoparticles with strong absorption in the near-IR spectral range (in the "water window"). The nanoparticles were incorporated in the interior of temperature-responsive poly(N-isopropylacrylamide-acrylic acid) microgels. Upon irradiation at lambda = 810 nm, hybrid microgel particles doped with Au nanorods underwent a strong deswelling phase transition. These photothermally responsive microgels can be used to carry and release small molecules (e.g., small protein molecules and drugs).     

25.

The reduction of methylene blue by sulfide ion in the absence and presence of oxygen: Simulation of the methylene blue-O₂?HS^?-CSTR oscillations     

Peter Resch  F. W. Schneider  Richard J. Field  Mária Burger 《Reaction Kinetics and Catalysis Letters》1990,42(2):189-200

A mechanism is discussed which reproduces in simulations the oscillations during the methylene-blue catalyzed reduction of O₂ by HS^– in a continuous-flow, strirred tank reactor (CSTR). It contains 14 reactions and is based on experiments and simulations of simpler reactions including the reduction of MB⁺ by HS^– in the absence and presence of O₂ and the reactions of H₂O₂ and O₂ with HS^–. All experiments on component reactions as well as the CSTR oscillations can be simulated by the same set of reactions and rate constants. The major dynamic feature of the mechanism is the competition for MB^. by the oxidizing agents O₂ and H₂O₂ and the reducing agents HS^– and HS^.. The species MB^. is the radical intermediate between the colored (MB⁺) and colorless (MBH) forms of methylene blue.     

26.

Insertion of CO2, CS2, and COS into iron(II)-hydride bonds     

Field LD  Lawrenz ET  Shaw WJ  Turner P 《Inorganic chemistry》2000,39(25):5632-5638

The reactions between cis-Fe(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2) (1) or cis-Fe(PP3)H2 (PP3 = P(CH2CH2PMe2)3) (2) and carbon dioxide (CO2), carbon disulfide (CS2), and carbonyl sulfide (COS) are investigated. At 300 K, additions of CO2 (1 atm), CS2 (2 equiv), and COS (1 atm) to 1 result in the formation of a stable transformato hydride, trans-Fe(dmpe)2(OCHO)H (3a), a trans-dithioformato hydride, trans-Fe(dmpe)2(SCHS)H (4a), and a trans-thioformato hydride, trans-Fe(dmpe)2(SCHO)H (5a), respectively. When CS2 and COS are added to cis-Fe(dmpe)2H2 at 195 K, a cis-dithioformato hydride, 4b, and a cis-thioformato hydride, 5b, respectively, are observed as the initially formed products, but there is no evidence of the corresponding cis-formato hydride upon addition of CO2 to cis-Fe(dmpe)2H2. Additions of excess CO2, CS2, and COS to 1 at lower temperatures (195-240 K) result in the formation of a trans-bis(formate), trans-Fe(dmpe)2(OCHO)2 (3b), a trans-bis(dithioformate), trans-Fe(dmpe)2(SCHS)2 (4c), and a cis-bis(thioformate), cis-Fe(dmpe)2(SCHO)2 (5c), respectively. trans-Fe(dmpe)2(SCHO)2 (5d) is prepared by the addition of excess COS at 300 K. Additions of CO2 (1 atm), CS2 (0.75 equiv), and COS (1 atm) to 2 at 300 K result in the formation of a thermally stable, geometrically constrained cis-formato hydride, cis-Fe(PP3)(OCHO)H (6a), a cis-dithioformato hydride, cis-Fe(PP3)(SCHS)H (7a), and a cis-thioformato hydride, cis-Fe(PP3)(SCHO)H (8a), respectively. Additions of excess CO2 and COS to 2 yield a cis-bis(formate), cis-Fe(PP3)(OCHO)2 (6b), and a thermally stable cis-bis(thioformate), cis-Fe(PP3)(SCHO)2 (8b), respectively. All complexes are characterized by multinuclear NMR spectroscopy, with IR spectroscopy and elemental analyses confirming structures of thermally stable complexes where possible. Complexes 3b and 5a are also characterized by X-ray crystallography.     

27.

Structure of [FeH(N2){(H5C2)2PCH2CH2P(C2H5)2}2]BPh4     

I. E. Buys  L. D. Field  T. W. Hambley  A. E. D. McQueen 《Acta Crystallographica. Section C, Structural Chemistry》1993,49(6):1056-1059

     

28.

Stabilisation of [Fe₂(CO)₉] and [Ru₂(CO)₉] bu substitution with bridging diphosphorus ligands     

Gerard de Leeuw  John S. Field  Raymond J. Haines  Beth McCulloch  Elsie Meintjies  Christiaan Monberg  Gillian M. Olivier  Praveen Ramdial  Clifford N. Sampson  Beate Sigwarth  Nick D. Steen  Kandasamy G. Moodley 《Journal of organometallic chemistry》1984,275(1):99-111

Reaction of [Fe₂(CO)₉] with a half molar amount of R₂PYPR₂ (Y = CH₂, R = Ph, Me, OMe or OPrⁱ; Y = N(Et), R = OPh, OMe or OCH₂; Y = N(Me), R = OPrⁱ or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe₂(μ-CO)(CO)₆{μ-R₂PYPR₂}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe₂(μ-CO)(C))₄{μ-R₂PYPR₂}₂] but under thermal conditions in the formation of the mononuclear species [Fe(CO)₃{R₂PYPR₂}]. Reaction of [Ru₃(CO)₁₂] with an equimolar amount of (RO)₂PN(R′)P(OR)₂ (R′ = Me, R = Prⁱ or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru₃(CO)₁₀{μ-(RO)₂PN(OR)₂}] which reacts further with excess (RO)₂PN(R′)P(OR)₂ on irradiation with ultraviolet light to afford the dinuclear compound [Ru₂(μ-CO)(CO₄{μ-(RO)₂PN(R′)P(OR)₂}₂]. The molecular structure of [Ru₂(μ-CO)(CO)₄{μ-(MeO)₂PN(Et)P(OMe)₂}₂], which has been determined by X-ray crystallography, is described.     

29.

Synthesis of the branched-chain sugar aceric acid: a unique component of the pectic polysaccharide rhamnogalacturonan-II     

Jones NA  Nepogodiev SA  MacDonald CJ  Hughes DL  Field RA 《The Journal of organic chemistry》2005,70(21):8556-8559

Described herein is the synthesis of 3-C-carboxy-5-deoxy-L-xylose (aceric acid), a rare branched-chain sugar found in the complex pectic polysaccharide rhamnogalacturonan-II. The key synthetic step in the construction of aceric acid was the stereoselective addition of 2-trimethylsilyl thiazole to 5-deoxy-1,2-O-isopropylidene-alpha-L-erythro-pentofuran-3-ulose (2), which was prepared from L-xylose. The thiazole group was efficiently converted into the required carboxyl group via conventional transformations. Aceric acid was also synthesized by dihydroxylation of a 3-C-methylene derivative of 2 followed by oxidation of the resulting hydroxylmethyl group. The C-2 epimer of aceric acid was also synthesized using thiazole addition chemistry, starting from L-arabinose.     

30.

An experimental study of the processγγ→π⁺π^?     

H. -J. Behrend  L. Criegee  J. H. Field  G. Franke  H. Jung  J. Meyer  J. H. Peters  O. Podobrin  V. Schr?der  G. G. Winter  et al. 《Zeitschrift fur Physik C Particles and Fields》1992,56(3):381-390

     

[首页] « 上一页 [1] [2] 3 [4] [5] [6] [7] [8] [9] [10] [11] 下一页 » 末  页»

	$\text{a}{}^3\text{Σ}{}^{\mathrm{+}}$	$\text{A}{}^1\text{Σ}{}^{\mathrm{+}}$	$\text{b}{}^3\text{Π}$	$\text{A′}{}^1\text{Π}$
$\text{T}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	16 596(3)	16 807.345(10)	17 502.6(10)	17 619.7(2)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	469.0(7)	499.620(19)	447.62(8)	447.95(22)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{x}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	1.48(4)	1.716(8)	2.287(12)	2.139(8)
$\text{ω}{}_{\mathrm{<mtext>e</mtext>}}\text{y}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^2\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$		2.14(9)		1.02(3)
$\text{B}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	0.2594(5)	0.2583908(26)	0.22426(16)	0.22385(16)
$\text{α}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^3\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$	1.44(5)	1.111(3)	1.18(4)	1.15(4)
$\text{γ}{}_{\mathrm{<mtext>e</mtext>}}\text{× 10}{}^6\text{(}\text{cm}{}^{\mathrm{?1}}\text{)}$		7.0(7)		?4.0(21)
$\text{R}{}_{\mathrm{<mtext>e</mtext>}}\text{(}\text{A}\text{?}\text{)}$	2.1294(20)	2.133512(11)	2.2901(8)	2.2922(8)

Hybrid microgels photoresponsive in the near-infrared spectral range

We report for the first time a photothermally responsive composite material based on polymer microgel particles doped with gold nanorods. We used the dependence of the longitudinal surface plasmon of the gold nanorods on their aspect ratio to synthesize nanoparticles with strong absorption in the near-IR spectral range (in the "water window"). The nanoparticles were incorporated in the interior of temperature-responsive poly(N-isopropylacrylamide-acrylic acid) microgels. Upon irradiation at lambda = 810 nm, hybrid microgel particles doped with Au nanorods underwent a strong deswelling phase transition. These photothermally responsive microgels can be used to carry and release small molecules (e.g., small protein molecules and drugs).     

The reduction of methylene blue by sulfide ion in the absence and presence of oxygen: Simulation of the methylene blue-O2?HS?-CSTR oscillations

A mechanism is discussed which reproduces in simulations the oscillations during the methylene-blue catalyzed reduction of O₂ by HS^– in a continuous-flow, strirred tank reactor (CSTR). It contains 14 reactions and is based on experiments and simulations of simpler reactions including the reduction of MB⁺ by HS^– in the absence and presence of O₂ and the reactions of H₂O₂ and O₂ with HS^–. All experiments on component reactions as well as the CSTR oscillations can be simulated by the same set of reactions and rate constants. The major dynamic feature of the mechanism is the competition for MB^. by the oxidizing agents O₂ and H₂O₂ and the reducing agents HS^– and HS^.. The species MB^. is the radical intermediate between the colored (MB⁺) and colorless (MBH) forms of methylene blue.     

Insertion of CO2, CS2, and COS into iron(II)-hydride bonds

The reactions between cis-Fe(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2) (1) or cis-Fe(PP3)H2 (PP3 = P(CH2CH2PMe2)3) (2) and carbon dioxide (CO2), carbon disulfide (CS2), and carbonyl sulfide (COS) are investigated. At 300 K, additions of CO2 (1 atm), CS2 (2 equiv), and COS (1 atm) to 1 result in the formation of a stable transformato hydride, trans-Fe(dmpe)2(OCHO)H (3a), a trans-dithioformato hydride, trans-Fe(dmpe)2(SCHS)H (4a), and a trans-thioformato hydride, trans-Fe(dmpe)2(SCHO)H (5a), respectively. When CS2 and COS are added to cis-Fe(dmpe)2H2 at 195 K, a cis-dithioformato hydride, 4b, and a cis-thioformato hydride, 5b, respectively, are observed as the initially formed products, but there is no evidence of the corresponding cis-formato hydride upon addition of CO2 to cis-Fe(dmpe)2H2. Additions of excess CO2, CS2, and COS to 1 at lower temperatures (195-240 K) result in the formation of a trans-bis(formate), trans-Fe(dmpe)2(OCHO)2 (3b), a trans-bis(dithioformate), trans-Fe(dmpe)2(SCHS)2 (4c), and a cis-bis(thioformate), cis-Fe(dmpe)2(SCHO)2 (5c), respectively. trans-Fe(dmpe)2(SCHO)2 (5d) is prepared by the addition of excess COS at 300 K. Additions of CO2 (1 atm), CS2 (0.75 equiv), and COS (1 atm) to 2 at 300 K result in the formation of a thermally stable, geometrically constrained cis-formato hydride, cis-Fe(PP3)(OCHO)H (6a), a cis-dithioformato hydride, cis-Fe(PP3)(SCHS)H (7a), and a cis-thioformato hydride, cis-Fe(PP3)(SCHO)H (8a), respectively. Additions of excess CO2 and COS to 2 yield a cis-bis(formate), cis-Fe(PP3)(OCHO)2 (6b), and a thermally stable cis-bis(thioformate), cis-Fe(PP3)(SCHO)2 (8b), respectively. All complexes are characterized by multinuclear NMR spectroscopy, with IR spectroscopy and elemental analyses confirming structures of thermally stable complexes where possible. Complexes 3b and 5a are also characterized by X-ray crystallography.     

Stabilisation of [Fe2(CO)9] and [Ru2(CO)9] bu substitution with bridging diphosphorus ligands

Reaction of [Fe₂(CO)₉] with a half molar amount of R₂PYPR₂ (Y = CH₂, R = Ph, Me, OMe or OPrⁱ; Y = N(Et), R = OPh, OMe or OCH₂; Y = N(Me), R = OPrⁱ or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe₂(μ-CO)(CO)₆{μ-R₂PYPR₂}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe₂(μ-CO)(C))₄{μ-R₂PYPR₂}₂] but under thermal conditions in the formation of the mononuclear species [Fe(CO)₃{R₂PYPR₂}]. Reaction of [Ru₃(CO)₁₂] with an equimolar amount of (RO)₂PN(R′)P(OR)₂ (R′ = Me, R = Prⁱ or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru₃(CO)₁₀{μ-(RO)₂PN(OR)₂}] which reacts further with excess (RO)₂PN(R′)P(OR)₂ on irradiation with ultraviolet light to afford the dinuclear compound [Ru₂(μ-CO)(CO₄{μ-(RO)₂PN(R′)P(OR)₂}₂]. The molecular structure of [Ru₂(μ-CO)(CO)₄{μ-(MeO)₂PN(Et)P(OMe)₂}₂], which has been determined by X-ray crystallography, is described.     

Synthesis of the branched-chain sugar aceric acid: a unique component of the pectic polysaccharide rhamnogalacturonan-II

Described herein is the synthesis of 3-C-carboxy-5-deoxy-L-xylose (aceric acid), a rare branched-chain sugar found in the complex pectic polysaccharide rhamnogalacturonan-II. The key synthetic step in the construction of aceric acid was the stereoselective addition of 2-trimethylsilyl thiazole to 5-deoxy-1,2-O-isopropylidene-alpha-L-erythro-pentofuran-3-ulose (2), which was prepared from L-xylose. The thiazole group was efficiently converted into the required carboxyl group via conventional transformations. Aceric acid was also synthesized by dihydroxylation of a 3-C-methylene derivative of 2 followed by oxidation of the resulting hydroxylmethyl group. The C-2 epimer of aceric acid was also synthesized using thiazole addition chemistry, starting from L-arabinose.