Journal of the Chemical Society Chemical Communications

Published by Royal Society of Chemistry
Online ISSN: 0022-4936
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Article
PIP This is a detailed description of 1 route to the chemical synthesis of PGs (prostaglandins) and their analogs in the laboratory. The chemical formula and chemical structure of each step in the chain is diagrammed. The aldehyde had served as intermediary in the synthesizing process in previous experiments. In this series of steps, the starting stage was the Prins reaction of norbornadiene and paraform-aldehyde in formic acid. Lactones were used as starting materials in the synthesis. Hydrolysis and oxidation were used to change 1 substance in the process into the next.
 
Article
The resolution of gossypol for the purpose of comparing the biologic action of (-)-gossypol with its naturally occurring antipode has attracted the attention of scientists. Recently the 1st successful resolution accomplished by chromatographic separation of the hexa-acetates of the condensation products of (+)-gossypol with (S)-1-methylphenethylamine followed by acid hydrolysis of the 2 main hexa-acetate, to give (+)- and (-)-gossypol with identical mp and alpha D values, was reported. Treatment of racemic gossypol with either (R)- or (S)-methylphenethylamine afforded yellow solids with mp 197-200 degrees C and m/z 753 (M + 1)+. By quick chromatography of the condensation products of either the (S) or (R) amine with (+)-gossypol on a silica column with diethyl ether-light petroleum as eluant, pure compounds were obtained. The compounds were assigned as (S)-amino-(+)-gossypol and (R)-amino-(-)-gossypol. These gossypols contained less than 5% of their antipodes. Although different in their antifertility action, the (+ or -), (+), and (-) isomers of gossypol demonstrate the same degree of inhibitory activity against the enzyme lactate dehydrogenase-X. Comparison of the antifertility action of the 3 isomers in male rats revealed that (-)-gossypol in half the dose of the (+ or -) isomer showed comparable activity, while the (+)-gossypol proved to be inactive.
 
Article
13 C-labelled lipids (enrichment 32%) have been isolated from wild-type yeast, Saccharomyces cerevisiae(x2180), grown on media containing sodium [2-13C]-acetate (50–60%); the 13C n.m.r. spectrum of 13C-enriched methyl palmitoleate is correlated with the natural abundance 13C resonance signals assigned using additive bond parameters and structural analogies with reference compounds.
 
Article
V2O5P2O5-based oxides were found to be effective as catalysts for the partial oxidation of propane, using gaseous oxygen as an oxidant. Acrylic acid was the sole product other than carbon oxides. The best results for the formation of acrylic acid are obtained with this Te/P/V atomic ratio; 0.10−0.15/1.15/1 oxide catalysts. The yield of acrylic acid attains 10.5 mol%. As the extent of the reaction increases, the selectivity steadily decreases, while the yield first increases and then attains a maximum at a propane conversion of about 50%. The rate of reaction increases with an increase in the concentrations of both oxygen and propane, while it remains almost unchanged with the addition of water vapor to the feed gas. On the other hand, for the formation of acrylic acid, higher concentrations of oxygen and water vapor, a lower concentration of propane, and a lower reaction temperature are found to be favorable.
 
Article
The green alga Botryococcus braunii, implicated in the formation of certain geological deposits, produces unusual isomeric C34H58 alkenes, botryococcene and isobotryococcene, during a particular physiological state. A structure for botryococcene is suggested, taking into account NMR techniques, oxidative degradation, and established biosynthetic principles. Botryococcene appears terpenoid in origin.
 
Article
The photo-induced isomerization of an aryl isocyanide in methanol into a cyanide received assistance from a strong electron donating substituent in the para-position; in aprotic solvents the rearrangement was inhibited.
 
Article
A short total synthesis of the bacterial coenzyme methoxatin (1) (4,5-dihydro-4, 5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylic acid) is described. The route involves the two step conversion of 4-acetamido-2-benzy1oxybenzaldehyde (5b) into methyl 6-acctamido-4-benzyloxyindole-2-carboxylate (7b) (74%), followed by regioselective annulation of the third ring (55%),and debenzylation and oxidation with benzoyl t-butyl nitroxide to give the tricyclic quinone triester (13) (methoxatin triester) (83%).
 
Article
The design and operation of a series of oxidative excited state photoelectrochemical half-cells is described, as is the application of one of them to the production of H2O2 and Br2 in separate cell compartments in acetonitrile solution. The basis for the half-cells is in the series of steps: (1) optical excitation of the metal-to-ligand charge transfer chromophore in complexes such as (bpy)Os(das)22+ (bpy is 2,2′-bipyridine; das is 1,2-bis-dimethylarsinobenzene), (2) reductive quenching of the excited states by N(p-C6H4Br)3 (NAr3), (3) scavenging of the reduced metal complex in acidic acetonitrile by O2 which gives H2O2 and builds up NAr3+ and (4) transfer of the oxidizing equivalents in NAr3+ through an external circuit to a dark anode compartment where oxidation occurs. In the H2O2/Br2 cell, Br− is oxidized to Br2 in the second compartment. A kinetic model developed earlier has been successfully applied to the (bpy)Os(das)22+ half-cell; this successfully predicts variations in photocharge with variations in chromophore, quencher and O2 concentrations, incident light intensity and added acid. In an air-saturated solution saturated with quencher the cell efficiency for the production of H2O2 and Br2 at high limiting concentrations of quencher is φ′cell = 0.85 ]+- 0.05 (equivalents of photoproducts per photon absorbed) at 25 °C. Under the same air-saturated conditions, the most efficient half-cell is based on the chromophore Ru(4,4′-(Co2Et)2bpy)32+ (4,4′-(CO2Et)2bpy is 4,4′-bis(carboethoxy)-2,2′-bipyridine) where φ′cell = 1.8 ± 0.5. φcell values in excess of unity provide evidence for a kinetic step in which the one-electron intermediate HO2 is reduced by NAr3 to give a second mole of NAr3+ per photon absorbed.
 
Article
Formaldehyde has been produced from methanol with high selectivity at 750 K in a continuous flow reactor over silicalites containing sodium ions. On the basis of the results obtained with the pulse reactor technique, it is concluded that the sodium ions in the silicalites are essential for the dehydrogenation of methanol, whereas the aluminum impurities play only a small role. The decomposition of formaldehyde has also been investigated at 670 K. Active sites for the decomposition would be transition metal impurities in the silicalites. These sites are assumed to be deactivated at the initial stage of the continuous flow reaction.
 
Article
The (–)-8-phenylmenthol ester of N-Boc-glycine is brominated with N-bromosuccinimide and the bromo-compound is reduced with tri-n-butyldeuteriostannane to give the chiral glycine derivative in high optical yield which upon hydrolysis yields the amino acid without racemisation.
 
Article
An efficient synthesis of disodium prephenate is described which illustrates the use of 5-ylidene-1,3-dioxalan-4-ones for the synthesis of acid labile α-keto acids.
 
Article
α-Methylene-β-lactams 3 were synthesized from the various 2-bromoallylamine derivatives 2 using a catalytic amount of Pd(OAc)2 or PD(acac)2 and PPh3, under 1–4 atom pressure of CO in good yields. Similarly, α-alkylidene-β-lactams 20 were synthesized from 3-alkyl-2-bromoallylamines 19, which were easily prepared from the olefins 14, in the same manner.
 
Article
Asymmetric reduction of prochiral aromatic ketones with the reagent prepared from (S)-(–)-2-amino-3-methyl-1,1-diphenylbutan-1-ol [(S)-(1)] and borane afforded the corresponding aromatic secondary alcohols in high optical (94–100% enantiomeric excess) and chemical (100%) yields.
 
Article
Oleanolic, maslinic, 3-epimaslinic, ursolic, and 2α-hydroxyursolic acids were isolated as their methyl esters from tissue cultures derived from Isodon japonicus Hara. All 13C NMR signals of the olean-12-enes and the urs-12-enes were assigned by chemical-shift comparisons with those of a number of derivatives and by various NMR techniques. The 13C-labeling patterns were elucidated with the 13C spectra of these triterpenes enriched with [4-13C]mevalonolactone and sodium [1,2-13C2]acetate. During the formation of the D- and E-ring systems, two rearrangements of the carbon skeleton for olean-12-enes and three rearrangements, including methyl migration from C-20 to C-19, for urs-12-enes were verified in the biosynthesis of triterpenes in the tissue cultures. The results were entirely in accord with Ruzicka's hypothesis for cyclization of squalene to β-amyrin and α-amyrin and excluded an alternative mechanism proposed for α-amyrin biosynthesis, including a 19,19-dimethyl intermediate. Moreover, the C-23 and C-30 methyl groups were derived from C-2 of mevalonate and the C-24 and C-29 methyl groups were derived from C-6 of mevalonate in both types of triterpenes. (3S)-2,3-Oxidosqualene was confirmed to be a precursor of 3α-hydroxytriterpene, as well as 3β-hydroxytriterpene.
 
Article
Starting from the Diels–Alder adduct (3) between 2-methoxycarbonyl-1,4-benzoquinone and cyclopentadiene, a modified Barborak's synthesis of D3-trishomocubane afforded (–)-2-(1S,3S,5R,6S,8R,10R)-D3-trishomocubaneacetic acid (11) whose esterification with 1,3,5,7-tetrakis(hydroxymethyl)adamantane (1) gave (–)-(2), the first organic molecule of T symmetry with known absolute configuration.
 
Article
DL-[4,5-13C2,6-14] Lysine is incorporated specifically, and via a symmetrical intermediate, into ring A of vertine (3) and lythrine (6); the cis- and trans-quinolizidinones, (9) and (10), are respectively and specifically, effective precursors for (3) and (6), and the corresponding mono-O-methyl ethers (11)–(14) are not utilized for alkaloid biosynthesis.
 
Article
The syntheses of optically active forms of triple and quadruple-layered [2,2]paracyclophanes are reported.
 
Article
The four possible stereoisomers of a new metabolite of vitamin D3, 25-hydroxycholecalciferol-26, 23-lactone, have been synthesised; we establish that the natural product has the 23R, 25S stereochemistry, and that it has <1% of the activity of vitamin D3 in bringing about intestinal calcium absorption.
 
Article
U.v. irradiation of the cis bicyclic αβ-unsaturated ketone (5) in diethyl Lg-(+)-tartrate afforded a 1 : 7 mixture of the cis(5) and the trans ketone (6) enriched in the (–)-enantiomer; Wolff–Kishner reduction of (6) yielded (–)-D2-bicyclo[8.8.0]octadec-1(10)-ene (7)(optical purity 0·5–1·0%) with the (R)- configuration.
 
Article
The hydrogenation of organic compounds with rare-earth intermetallic hydrides has been investigated. Alkynes, alkenes, aldehydes, ketones, nitriles, imines, and nitro compounds are hydrogenated in excellent yields with LaNi6H6 or LaNi4.5Al0.5H5 at 0-60°C. The present hydrogenation method has the following characteristic features. (1) The intermetallic compounds (alloys) are not poisoned by compounds containing an amino group or a halogen atom. (2) The alloys can be used repeatedly without decrease in activity. (3) The reaction conditions are mild, and selective hydrogenations of some organic functional groups can be achieved. The reaction mechanism of this hydrogenation is briefly discussed in terms of stereochemistry and H/D exchange reactions.
 
Article
Tungstate-catalysed oxidation of 1,2,3,4-tetrahydroquinolines with hydrogen peroxide gives 1-hydroxy-2-oxo-1,2,3,4-tetrahydroquinolines highly efficiently.
 
Article
The π aromatic aldehyde complexes [(η5-C5H5)Re(NO)(PPh3)(η2-OCHAr)]+BF4- (1+BF4-; Ar = a, C6F5; b, 4-C6H4CF3; c, 4-C6H4Cl; d, C6H5; e, 4-C6H4CH3; f, 4-C6H4CH2CH3; g, 4-C6H4OCH3) exist as mixtures of configurational diastereomers (RS,SR/RR,SS or π/π‘) that differ in the OC enantioface bound to rhenium. Under standard conditions (0.000 71 M, CH2Cl2, 173 K), π/π‘ equilibrium ratios are 97:3, 89:11, 84:16, 80:20, 76:24, 79:21, and 74:26, respectively. Steric interactions between the aryl groups and cyclopentadienyl ligands destabilize the π‘ isomers. The crystal structures of (RS,SR)-1a−c,f+PF6- and (RS,SR)-1d+SbF6- show that the distances between the rhenium and carbon stereocenters (Å, a/b/c/d/f: 2.157(5)−2.161(9), 2.172(4), 2.176(4), 2.182(6)−2.188(9), 2.184(5)−2.199(6)) increase as π/π‘ ratios decrease. Stronger π accepting aldehydes give shorter bonds and higher chiral recognition. The aliphatic aldehyde complexes [(η5-C5H5)Re(NO)(PPh3)(η2-OCHR)]+BF4- exhibit higher π/π‘ ratios (R = CH3, 99.0:1.0; CH2CH3, 99.8:0.2; CH2CH2CH3, 99.5:0.5; CH(CH3)2 and C(CH3)3, >99.9:<0.1), and possible rationales are given. The π/π‘ ratios increase at higher concentration or lower temperature, and vary slightly with counteranion (BF4- > PF6- ≥ SbF6-).
 
Article
Alkylation of lithium dihydroanthracenylide by (–)R-6-chloro-2,6-dimethyloctane occurs with racemization and only a small degree of inversion of configuration, in agreement with the main pathway involving the previously proposed radical–radical anion combination.
 
Article
Two enantio couples of terminal C-glycopyranosyl-alpha-amino acids, namely the aminopyranuronic acids L-9, D-9 and L-10, D-10, have been synthesized from the serine-derived pair L-2, D-2 by exploiting enantiomerically pure butenolide intermediates 3 and 4. The key synthetic steps involved the sequential antiselective cis dihydroxylation of the butenolide double bond and the clean furanose-to-pyranose ring expansion to construct the sugar skeleton with the proper stereochemistry. In our best performance, homogeneous L-9 was prepared from L-2 in four steps and 10 reactions in 20% overall yield.
 
Article
Ru3(CO)12 (1) and Ru(CO)3(PPh3)2 (2) catalyze the reductive carbonylation of nitrobenzene and of substituted aromatic mononitro compounds to give the corresponding methylcarbamates, in toluene-methanol, at 160-170 °C and 60 atm, with high selectivity, in the presence of NEt4+Cl- as cocatalyst. Compound 1 also catalyzes the conversion of 2,4-dinitrotoluene into the corresponding dicarbamate although less efficiently. The effects of CO pressure, reaction temperature, and amount and nature of the added alcohol and cocatalyst have been studied. The mechanism of the reaction catalyzed by 1 has been investigated by studying the reactivity and catalytic activity of possible intermediates.
 
Article
Treatment of p-tert-butylphenyl 4,6-di-O-benzyl-2,3-dideoxy-α-d-erythro-hex-2-enopyranoside (1aα) or the 4,6-di-O-(tert-butyldimethylsilyl) analogue (1bα) with various functionalized arylmagnesium bromides in the presence of a catalytic amount of PdCl2(dppf) at 25 °C in THF afforded the corresponding unsaturated C-arylglycosides 2−14 having the α-configuration in quite good yields. Benzyl-, allyl-, and vinylmagnesium bromides gave also the corresponding unsaturated α-C-glycosides 15−18, although in lower yields. When the same reaction was performed in the presence of NiCl2(dppe) as the catalyst at −40 °C, only the formation of the corresponding unsaturated C-arylglycosides having the β-configuration was observed. As expected, reaction of phenylmagnesium bromide with p-tert-butylphenyl 4,6-di-O-benzyl-2,3-dideoxy-β-d-erythro-hex-2-enopyranoside (1aβ) in the presence of NiCl2(dppe) gave only the unsaturated β-C-phenylglycoside 2aβ, while palladium-catalyzed reaction led to the preponderant formation of C-phenylglycoside 2aα. Reaction of PhMgBr with p-tert-butylphenyl 4-O-benzyl-2,3,6-trideoxy-α-l-erythro-hex-2-enopyranoside (20) afforded stereospecifically the unsaturated α- and β-C-phenylglycoside 25 in the presence of PdCl2(dppf) and NiCl2(dppe), respectively.
 
Article
Pentafluoronitrosobenzene undergoes an "ene"-type reaction with a variety of olefins. When triethyl phosphite is added to the olefin before the addition of the nitroso compound (inverse addition), pentafluorophenylnitrene is formed which adds stereospecifically to a number of olefins to give the corresponding aziridines. The possibility of a 1,3-dipolar addition of the nitrene precursor followed by elimination of triethyl phosphate has been discounted. Pentafluorophenylnitrene, generated photochemically from the azide, behaves analogously, but thermal decomposition of the azide in the presence of olefins gives products arising from an initial 1,3-dipolar adduct. 4-Azidotetrachloropyridine behaves similarly but the derived nitrene is less electrophilic.
 
Article
Several cobalt nitrosyl complexes, CoL 4NO, reacted with oxygen in the presence of nitrogen and phosphorus bases to yield the corresponding nitro compounds, CoL 4(NO 2)B, where L 4 is the tetradentate dianions N,N′-ethylenebis(acetylacetoniminate), N,N′-ethylenebis(monotnioacetylacetoniminate), N,N′-ethylenebis(benzoylacetoniminate), N,N′-ethylenebis(salicylideniminate), and two bidentate dimethyldithiocarbamate anions. Exposing an acetonitrile solution of nitrosylbis(ethylenediamine)cobalt diperchlorate to oxygen resulted in the precipitation of [Co(en) 2(CH 3CN)NO 2](ClO 4) 2. The nitro products, CoL 4(NO 2)B [where B = pyridine, C 3H 7NH 2, and P(CH 3) 2(C 6H 5)] and [Co(en) 2(CH 3CN)NO 2](ClO 4) 2 were isolated and characterized by elemental analyses and infrared, proton magnetic resonance, and electronic spectra. Kinetic studies revealed that the rates of reaction have a first-order dependence on the concentrations of oxygen and the cobalt nitrosyl complexes. The reaction rates increase with increasing base concentration but reach a limiting rate at high base concentrations. A possible mechanism for the reaction is proposed and discussed.
 
Article
A series of complex metal hydrides of zinc with composition MnZnmH2m+n, where M = Li, Na, or K, has been synthesized by reacting an appropriate "ate" complex of zinc (MnZnmR2m+n) with either LiAlH4, NaAlH4, or AlH3. The 1:1, 2:1, and 3:1 complexes of methyllithium and dimethylzinc yielded LiZnH3, Li2ZnH4, and Li3ZnH5 when allowed to react with lithium aluminum hydride in diethyl ether. The reaction of potassium hydride with dimethylzinc in 1:1 and 1:2 ratios in tetrahydrofuran yielded potassium dimethylhydridozincate [KZn(CH3)2H] and potassium tetramethylhydridodizincate [KZn2(CH3)4H]. KZn2H5 resulted when either KZn(CH3)2H or KZn2(CH3)4H was allowed to react with AlH3 in tetrahydrofuran; whereas, KZnH3 was obtained from the reaction of KZn(CH3)2H with lithium aluminum hydride in the same solvent. Both the 1:1 and 1:2 complexes of sodium hydride with dimethylzinc gave NaZnH3 when allowed to react with sodium aluminum hydride in tetrahydrofuran. These reactions are presented as examples of a new and general route for the preparation of complex metal hydrides by the reaction of "ate" complexes with complex metal hydrides of aluminum or AlH3.
 
Article
Irradiation of phenyl vinyl ether in the presence of aromatic compounds, such as dimethyl terephthalate, methyl benzoate, or benzonitrile, gives a mixture of trans- and cis-head-to-head cyclodimers of the olefin.
 
Article
An all-electron, first-principles SCF-XαSW calculation of the electronic structure of Mo2Cl84- is used to discuss the nature of Mo-Mo and Mo-Cl bonding in this ion and its electronic spectrum. The upper valence region of the energy-level diagram (-0.04 to -0.33 hartree) contains, in order of increasing energy, Mo-Cl bonding, Cl nonbonding, and Mo-Mo σ, π, and δ bonding levels. The δ level is the highest occupied; above it are empty δ*, two dx2-y2, π*, and σ* antibonding levels. The Mo and Cl character in the upper valence levels is made up almost entirely from 4d and 3p functions, respectively; eight nearly pure Cl 3s levels in the range -0.70 to -0.72 hartree complete the valence region, and no orbitals having large amounts of Mo 5s or 5p character are found. The d-like levels in Mo2Cl84- and hypothetical MoCl42- are compared. The σn levels postulated by Cotton to lie in the neighborhood of the δ* level are not found; otherwise the ordering of metal-metal bonding and antibonding levels agrees completely with Cotton's qualitative proposals. Contour maps of the σ, π, and δ wave functions are presented, showing them to be essentially simple overlaps of 4dz2, 4dxz,yz, and 4dxy orbitals, respectively, on the metals. The predicted electronic spectrum is in good agreement with the experimental solid-state spectrum of K4Mo2Cl8 · 2H2O. The two well-resolved peaks observed at 18.8 and 31.4 kcm-1 are assigned to dipole-allowed δ → δ* and π → dx2-y2 transitions, respectively. The strong unresolved absorption above 34 kcm-1 is believed at least partially due to some combination of Cl → δ* charge-transfer and π → π* transitions. The weak band at ca. 24 kcm-1 is apparently due to one or both of the dipole-forbidden π → δ* and δ → dx2-y2 transitions. The applicability of the energy-level diagram for Mo2Cl84- to other dimeric complexes of D4h symmetry is discussed.
 
Article
Analysis of the microwave spectrum shows the skeletal molecular structure of CB5H7 to be a distorted octahedral form with a face containing three long B–B bonds, and there is further evidence that a hydrogen atom is located in or above the octahedral face.
 
Article
(+)-Milbemycin β3(1) was prepared by total synthesis from (6S,8R,9S)-methyl 8,9-dimethyl-4-oxo-1,7-dioxaspiro[5.5]undeco-2-ene-2-carboxylate (2), (4R,6R)-4-methyl-6-phenylsulphonyl-(E)-hept-2-en-1-ol (3a), and 2-ethyl-4-methoxy-5-methylbenzoic acid (4) using Julia–Lythgoe and benzylic anion chemistry to establish the carbon framework and a Mitsunobu reaction to close the lactone ring.
 
Article
The thermal and anionic rearrangements of trans-1-vinylcyclotridec-3-en-1-ol compounds substituted in the α and β vinyl positions have been examined to determine whether the substituents can be used to control the periselectivity. For the anionic rearrangements, trimethylsilyl groups were found to be unsuitable, and terminal vinyl methyl or isopropyl groups did not provide a useful selectivity. Under thermal conditions, either a terminal trimethylsilyl or methyl gave high periselective control favoring the 1,3-shift siloxy Cope ring expansion relative to the 3,3-shift. This was used in a new synthsis of muscone.
 
Article
The oxidative degradation of [N(PPh3)2]3[Mnilll(CN)6] leads to the isolation of the unprecedented [C12N12]2- dianion, which is characterized by single-crystal X-ray diffraction and spectroscopic techniques. Journal Article
 
Article
The anodic oxidation of 1,2,2,2-tetraphenylcyclopropane leads to 1,1,3-triphenylindene or tetraphenylallene depending on the basicity of the medium.
 
Article
Whereas the 1 : 1 reaction of (2-cupriobenzyl)dimethylamine (RCu) with 1,2-bis(diphenylphosphino)ethane (diphos) affords the 1 : 1 complex RCu(diphos), 1 : 2 reaction results in cleavage of the C(alkyl)–P bond with formation of Ph2PCu(diphos)(solv), RH, and Ph2PCH = CH2.
 
Article
The quadridentate N-donor ligands (R)(S)-1,2-[(6-R-2-C5H3N)C(H)N]2–cyclohexane (R = H, Me), upon reaction with [M(O3SCF3)](M = AgI or CuI), behave as bridging di-bidentate ligands to form dimeric complexes such as the title complex for which an X-ray crystal structure was obtained; 3J(107,109Ag-1H) is observed in the 1H n.m.r. spectra of the dinuclear [Ag2L2]2+ cations.
 
Article
Reaction of [([eta]5-C5Me5)(CO)2Fe–P[doublebond]P–MeS*] 1 (Mes*= 2,4,6-But3C6H2) with 1,2,4-triazoline-3,5-diones [N[doublebond]N - C(O)N(R)C(O)] 2 (a: R = Ph; b: R = 4-EtOC6H4) in benzene at ambient temperature affords the first 1,2-diaza-3,4-diphosphetidines as part of the bicyclic compounds 4, whereas in diethyl ether solution the twelve-membered macrocycle 5 is obtained.
 
Article
In an aqueous solution of sodium hydrosulphide at room temperature, 4-(1,2,4-triazol-1-yl)-1-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)pyrimidin-2(1H)-one, prepared from uridine, is converted into the 4-thiopyrimidin-2(1H)-one derivative which can be deacetylated to yield 4-thiouridine.
 
Article
Reaction of [([eta]5-C5Me5)(CO)2 Fe–P(SiMe3)–PC(SiMe3)2]3 with (Z-cyclooctene)Cr(CO)5 affords the [eta]3-1-ferra-2,3-diphosphaferrocene complex {[([eta]5-C5Me5)(CO)2 Fe–P[doublebond]P–C(SiMe3)3]Cr(CO)4}4 and the first 1,2-diphosphaferrocene {([eta]5-C5Me5)[[eta]5-1,2-P2C3(OSiMe3)2(SiMe3)Cr(CO)5]Fe}5, the molecular structures of which have been determined by X-ray analysis.
 
Article
The cycloaddition of 8-styrylcyclohepta[b]pyrroles with dimethyl acetylenedicarboxylate give the 7H-6a-azacyclobuta[j]cyclopenta[1,2,3-cd]azulene ring system, which rearranges thermally into the 3H-2a-azacyclopenta[cd]azulene ring system.
 
Article
Very similar syn-anti-adduct ratios were observed when 1,2,3,4,5- pentamethylcyclopentadiene reacted with a variety of (Z)-ethylenic dienophiles, suggesting that in the exo region the transition-state geometries are very similar.
 
Article
The reaction of oxamidrazone with sulfur dichloride affords 4,4'-bis(1,2,3,5-dithiadiazolium) dichloride, which can be reduced with triphenylantimony to the corresponding bis(1,2,3,5-dithiadiazolyl) diradical; the solid state structure and transport properties of the dimer [S2N2CCN2S2]2 are reported.
 
Article
The reaction of N,N,N'-tris(trimethylsilyl)formamidine with SeCl2 affords 1,2,3,5-diselenadiazolium chloride, which can be reduced with triphenylantimony to the corresponding diselenadiazolyl radical [HCN2Se2]·; the solid state structure and conductivity of the dimer [HCN2Se2]2 are reported.
 
Article
Diphenylketene (2) undergoes [4 + 2] cycloadditions with the s-cis fixed diene (1) to give the dihydropyran (3) and the cyclohexenone (4).
 
Article
1-Thiocyanatobuta-1,3-dienes react with strong dienophiles to produce directly the rearranged products of type ( 6 ) via a combination of a Diels-Alder reaction with a [3,3] sigmatropic shift.
 
Article
Buta-1,3-dienyl thiocyanic acid ester reacts with acryloyl chloride in presence of Lewis acid catalysts to produce directly the rearranged product of type 3b via a combination of a Diels-Alder reaction with a [3,3] sigmatropic shift; the 1,4-substituted cyclohexene is easily transformed into the 2-azabicyclo[2.2.2]oct-5-ene derivative 6b , which has been used as precursor for the synthesis of the Ibogamin skeleton.
 
Article
Reaction of ([eta]5C5Me5)(CO)2 FeP(SiMe3)2 with three equivalents of Cl–P[doublebond]C(SiMe3)2 affords the first 3-methanediyl-1,3,5,6-tetraphosphabicyclo[3.1.0.]hex-2-ene 7, the molecular structure of which has been determined by X-ray analysis.
 
Top-cited authors
Donald Bethell
  • University of Liverpool
Mathias Brust
  • University of Liverpool
David Schiffrin
  • University of Liverpool
Michael Lappert
  • University of Sussex
Robin Whyman
  • University of Liverpool