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1.
Two minor lipid components of the brown seaweed were characterized as (all Z) - 5′,7′-dihydroxy-2′-nonadeca-4,7,10,13,16-pentenyl-chrome chromone () and 5′,7′-dihydroxy-2′-pentadecylchrome (). 相似文献
2.
Deactivation rate constants of spin-orbital excited Br atoms in the reactions Br(2P) + O2 → Br(2P) + O2 (k1), and Br(2P) + NO → Br(2P) + NO (k4) have been measured with a photodissociative IBr laser on the electronic transition 2P?2P in the Br atom (λ = 2.7 μm). The values obtained are (6.4 ± 1.8) × 10?14 cm3 s?1 and (1.9 ± 0.6) × 10?12 cm3 s?1, respectively. Comparison with published data leads to the conclusion that, contrary to a widely accepted point of view, the high rate constants for the quenching of excited halogen atoms are due to resonant energy transfer processes and not to the paramagnetic nature of the quencher. 相似文献
3.
R. Schwesinger K. Piontek W. Littke O. Schweikert H. Prinzbach C. Krüger Y.-H. Tsay 《Tetrahedron letters》1982,23(24):2427-2430
According to X-ray crystal structure analyses “cis-benzenetrisimine” () and “cis-benzenetrioxide” () act as tridentate ligands in their 2:1- and 4:1-complexes (Co(C6H9N3)2(NO3)3) and (Ba(C6H6O3)4(ClO4)2), resp. The latter is the rare example of an organic complex with the (approximate) T-symmetry. 相似文献
4.
Adenosine cyclic 3′,5′-phosphoramidate was synthesized by reacting adenosine cyclic 3′,5′-phosphate with POCl3, in trimethyl phosphate for 1 h at O°C, followed by in situ treatment of the reaction mixture with a suspension of (NH4)2CO3 in anhydrous DMF or pyridine or DMF/pyridine mixture for 30 min at 25° C. Diastereoisomers (P)- and (P)- the relative quantities of which depended on the solvent of (NH4)2CO3 treatment, were separated by reversed phase partition chromatography. Hydrolysis of (RP)- and (SP)- proceeded with predominant (90% in 0.1 N HCl, 100% in 0.1 N NaOH) -P-O-C bond breaking. 相似文献
5.
The production of I(2P) in the photolysis of CH2I2 has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm?1 correlate with I(2P) whilst those at 34700 and 40100 cm?1, which correlate with I(2P), give final 2P/2P ratios of 1.75 and 1.1, respectively, after curve crossing. 相似文献
6.
A new C3-unit substitution reaction at C-4 position of 4- acetoxyazetidinone derivative ( and ) by tetraallyltin () in the presence of 1/10 eq. of BF3-ether in methylene chloride is described. From 4-allylazetidinone derivative () via ylid intermediate () dethiathienamycin () was synthesized. 相似文献
7.
Combination of ()-4--butyldimethylsiloxy-2-cyclopentenone, ()-()-3--butyldimethylsiloxy-1-iodo-1-octene, and 6-methoxycarbonyl-2-hexynal via the tandem organo-copper conjugate addition—aldol reaction procedure leads directly to a 5,6-dehydroprostaglandin E2 derivative, which can be transformed to a variety of chiral primary prostaglandins in a stereoselective manner. 相似文献
8.
Previous (1) work on ternary chalcopyrite solid solution formation has shown that the difference in end point axial ratios () is an important factor in determining the extent of mutual solubility. It was concluded that when complete solid solubility will not occur. In this work it is shown that complete solid solution formation in the systems AgAlS2AgInS2 (), AgGaS2AgInS2 () and AgAlSe2AgInSe2 () does occur. This shows that the value of as an upper limit for solid solution formation can be approached closely. 相似文献
9.
J.R. Wiesenfeld 《Chemical physics letters》1973,21(3):517-520
The rate coefficients for the collisional deactivation of Tl(62P) by several gases has been determined at 300°K. This data is compared with that previously obtained at higher temperatures and the Arrhenius parameters calculated. Both the overall rate coefficients and temperature effects display trends similar to those observed for 1(52P) relaxation. The deactivation of Tl(62P) by O2 is shown to proceed by a process involving an equilibrium with Tl(62P) and electronically excited oxygen, probably O2(1Δg). 相似文献
10.
H. Krause K. Sille H.-D. Hausen J. Weidlein 《Journal of organometallic chemistry》1982,235(3):253-264
Reactions of urotropine (C6H12N4) with trimethylmetal derivatives of Al, Ga, In und Tl in various () molar ratios lead to stable and monomeric , or adducts in good yields, but no addition product could be isolated. The vibrational spectra (IR and Raman) of all compounds are recorded and partly assigned. Some characteristic frequencies of the C6N4-skeletons clearly show the symmetry changes in the series of the → → adducts (C3ν → C2ν → C3ν). The X-ray structure determinations of C6H12N4·.GaMe3 (MeCH3) and C6H12N4·.2GaMe3, are in good agreement with the vibrational spectra. Both compounds crystallize in monoclinic space groups (P21 and C2/c). The GaN distances are around 214 pm, and the values for the C6N4-skeletons are not significantly different from those for free urotropine. 相似文献
11.
By means of a time of flight technique, using high temperature surface ionization, we have been able to measure the internal energy of atoms formed in the photodissociation of KI at wavelengths between 265 and 335 nm. At all wavelengths only ground state K(2S) is formed. Between 265 and 295 nm iodine is solely formed in the excited I(2P) state, above 305 nm only in the ground state I(2P). 相似文献
12.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献
13.
Formaldehyde dimethyl dithioaoetal S,S-dioxide () reacted uith an alkyl bromide or a 2-alkenyl bromide () under phase-transfer sonditions using 50% aq. NaOH to give an alkyl or 2-alkenyl derivative of , whereas, in the reaction with in the presence of Kg2CO3KI in HMPA, formed a 1-alken-3-yl derivative. Transformation of these products into the corresponding carboxylio esters uae also described. 相似文献
14.
The cycloaddition of α,β-epoxyaldehydes or ketones () with the ketene acetal MeHC=C(OMe)2 () gives epoxyoxetanes () in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones () via the epoxy esters and trihydroxy esters (). The lactones appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones () and 3-methyl-5-ylidene-2-5H-furanones () 相似文献
15.
The reaction of Pt(PPh3)4 with CH2Cl1 in benzene yields the cationic ylide complex -[Pt(PPh3)2(CH2PPh3)Cl]I in high yield. This complex has been converted to -[(PPh3)2(CH2PPh3)X]X (X Br or I) by reaction with LiBr or NaI. Reaction of -[Pt(PPH3)I]I with iodine yields -[Pt(PPh3)2(CH2PPh3)I]I3. Nmr data are given in support of the suggested structures. 相似文献
16.
The RPX2·AlX3 complex () reacts with unsaturated ketones and imines to give novel 7-oxa and 7-aza-2-phosphabicyclo[2.2.1]heptanes (compounds and respectively).A new 1,3-dipolar addition of (CH3)2 CCH2P?XR to nArN=C=S was disclosed resulting in the formation of the 2-imino-1,3-thiaphospholanes (). 相似文献
17.
Oxidation of benzotropylium () fluoborate with Na2O2 and KO2 gives the benzotropones, and , as the major products with no naphthalene () or other ring contracted products formed. Oxidation with -chloroperoxybenzoic acid produces a small amount of naphthaldehydes ( and ) and even less naphthalene, a long with the benzotropones, while oxidation with H2O2 and -butyl peroxyacetate gives slightly more of the ring contracted naphthaldehydes than benzotropones, in addition to a small quantity of naphthalene. All reactions produce some 1,2-benzotropilidene () 相似文献
18.
Vacuum UV emission from the products of quenching ofAr(3Po) and Ar(3P2) by several reagents has been compared. The large differences suggest that Ar(3Po) and Ar(3P2) preferentially yield respectively the D() and B() excited states of ArBr★ or ArCl★, which show specific, but very different, predissociation patterns. 相似文献
19.
Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride () and 2-(trichloromethylmercapto)pyridine (). Neither a direct reaction of pyridine with CF3SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF3S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF3)2 yield 1:1-adducts () only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF3SCl to give 3-(trifluoromethylmercapto)pyridine (); in addition a disubstituted product can be identified massspectroscopically. 1H- and 19F-NMR-spectra are reported. 相似文献
20.
Fumie Sato Hiroaki Ishikawa Yoshihiko Takahashi Masatoshi Miura Masao Sato 《Tetrahedron letters》1979,20(39):3745-3748
SiO2-supported titanium chloride () and polystyrene-supported titanocene dichloride () and () were synthesized. These heterogenized titanium compounds are excellent catalysts for hydroalumination of olefins. 相似文献