The structure of a triosmium carbonyl cluster-phenylarsine oxide derivative

The reaction between the dihydride of decacarbonyltriosmium [H₂Os₃(CO)₁₀] and phenyl arsine oxide (PAO) in benzene yields only one product [Os₃(O)₉(μ-H){μ-PhAs(O)OAsPh}] (1), which is characterized by high resolution mass spectrometry (HRMS), Fast Atomic Bombardment Mass Spectrometry (FAB)⁺, IR, ¹H and ¹³C NMR, and single crystal X-ray diffraction. The solid state X-ray diffraction study of compound (1) shows that the molecule is polycyclic and has an osmium triangle with a bridging hydride bonded to a PhAs(O)-O-AsPh ligand.     

Colloidal silver nanoparticles stabilized by a water-soluble triosmium cluster

Silver nanoparticles stabilized by the water soluble triosmium cluster Os₃(μ-H)(CO)₁₀S(CH₂)₁₀COO]Na were prepared by both photochemical and chemical reduction of silver nitrate. The silver nanoparticles were characterized by UV-Vis spectroscopy and high resolution TEM. The particles obtained by chemical reduction showed remarkable stability.     

Evidence for a double intramolecular trimethylsilyl rearrangement

A double trimethylsilyl rearrangement ion, m/z 287, C₆H₅S(OSi(CH₃)₃)₃, was observed in the isobutane chemical ionization mass spectrum of 3-trimethylsilyl-9-(2-trimethylsilylethylthio)-1-phenyl-3-phenylsulfonylnonane. The daughter mass spectrum of the protonated molecule produced the rearrangement ion, m/z 287, suggesting that the double trimethylsilyl rearrangement occurred intramolecularly.     

Fragmentation of a novel marine peptide, plicatamide, involves an unusual gas-phase intramolecular rearrangement

During our characterization of plicatamide 1, a modified octapeptide: Phe-Phe-His-Leu-His-Phe-His-dc deltaDOPA (where dc deltaDOPA = decarboxy-(E)-alpha,beta-dehydro-3,4-dihydroxyphenylalanine) from the blood cells of the ascidian Styela plicata, we noted a series of fragment ions from the [M + H]+ ion which could not be assigned. There was no evidence in the 1H NMR spectrum to support an alternative molecular structure and the series of fragment ions were not present in the tandem mass spectrometry analysis of the [M + Na]+ ion. In addition, there was no evidence that the sample was a mixture of isobaric compounds. We propose that an unusual C-terminal to N-terminal rearrangement is responsible for the series of fragment ions from the [M + H]+ ion. This rearrangement was not observed in peptide analogs of plicatamide which did not contain the dc deltaDOPA at the C-terminus suggesting that this moiety is critical for the rearrangement. The proposed reaction is analogous to that recently reported by Vachet et al. involving a fragment ion formed from leucine enkephalin.     

Double activation of the diphosphinite pincer proligand by a triosmium carbonyl cluster

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A zwitterionic triosmium cluster bearing a metallated azulene ligand coordinated perpendicularly as an alkylidene bridge

The cluster [Os₃(CO)₁₀(MeCN)₂] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os₃(μ-H)(μ₂-η¹-C₁₀H₇)(CO)₁₀] 1 which was shown by its X-ray crystal structure to contain the C₅ ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a μ-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os₃(μ-H)₂(μ₃-η¹:η¹:η¹-C₁₀H₆)(CO)₉] 2.     

Novel rearrangement reaction of a 6,14-endoethanomorphinan derivative to a benzomorphan derivative

Treatment of 7α-hydroxymethylendoethenomorphinan derivative with trifluoromethanesulfonic anhydride at rt and subsequent toluene reflux afforded a novel lactone by rearrangement reaction. The skeleton of the lactone is analogous to that of the benzomorphan like pentazocine, which is a useful analgesic. The rearrangement reaction opens the door to a facile synthesis from the 4,5-epoxymorphinans to the benzomorphan derivatives. On the basis of careful examination of the reaction intermediates, a reaction mechanism was proposed.     

A novel oxamide rearrangement

An efficient, base-induced rearrangement of 2-[(1,2-dioxo-2-(methylamino)ethyl)phenylamino]benzoic acid methyl ester ( 7a ) to the isomeric 2-[(1,2-dioxo-2-(phenylamino)ethyl)methylamino]benzoic acid methyl ester ( 27a ) is described. This novel rearrangement must proceed through a spiro intermediate wherein benzoate is acting as a Michael receptor. When 2-[(1,2-dioxo-2-(methylamino)ethyl)methylamino]benzoic acid methyl ester ( 28 )-an oxamide which would produce a degenerate spiro intermediate — was subjected to rearrangement conditions, the product obtained was 1,3-dimethyl-2,4-(1H,3H)quinazolinedione ( 29 ). This latter transformation may have proceeded via a benzodiazepinetrione intermediate.     

Trapping a pseudo-Hofmann rearrangement on a ruthenium cluster

In the clusters [Ru3(micro(3)-NPPh(3))(micro(3)-OSiMe(3))(micro-X)(micro(C,O)-OC[double bond]NPPh(3))(micro-CO)(CO)6] (X = NCO, 2; X = Cl, 3), which were prepared by a pyrolytic reaction of Ph(3)PNSiMe(3) with Ru(3)(CO)12, the ligands result from a cluster-mediated pseudo-Hofmann rearrangement involving the micro-NCO, micro(C,O)-Ph(3)P[double bond]N-CO and micro(3)-NPPh(3) fragments.     

A novel acid-catalyzed rearrangement of cyclobutanols

Under acid-catalysis 7-arylbicyclo[3.2.0]hept-2-en-6-ols rearrange to diarylmethanes and cyclopenteno-annelated polycyclic aromatic hydrocarbons.     

Synthesis and crystal structure of a new triosmium alkylidyne carbonyl cluster containing a chiral ferrocenylphosphine ligand

The synthesis, spectroscopic characterization and X-ray crystal structure of a new chiral triosmium alkylidyne carbonyl cluster, (R,S)-[Os3(mu-H)2(CO)9{mu3-CPPh2(eta(5)-C5H4)Fe(eta(5)-C5H3(PPh2)CH(Me)NM(2)}] (1) are described. Compound 1 crystallizes in the non-centrosymmetric space group P2(1) and its absolute configuration has been established.The structure consists of an Os3C metal core with one of the PPh2 moieties of the chiral ferrocenylphosphine bonded to the apical alkylidyne carbon atom to give a zwitterionic cluster complex, reminiscent of the phosphorus ylide.     

An intramolecular anionic fries rearrangement of N-acylphenothiazines

Certain 2-substituted N-acylphenothiazines undergo a rapid intramol≐cular N→C migration on reaction with lithium N,N-dialkylamides at −78°. Preliminary studies of the scope and mechanism of this anionic version of the Fries rearrangement are reported.     

A novel palladium-catalyzed intramolecular redox reaction

[reaction: see text] A new type of palladium-catalyzed redox reaction is described, forming enones from 2-(2-bromobenzyl)-ketones with an overall loss of HBr. The scope and limitations of the reaction are demonstrated by a series of cyclic and acyclic substrates. The mechanism most probably involves the formation of an intramolecular arylpalladium enolate and is related to the oxidation of silyl enol ethers with palladium acetate.     

Stereoselective intramolecular hydrogen abstraction by a chiral benzophenone derivative

An unprecedented stereoselective photoreduction of a chiral BZP is observed in steady state as well as in time-resolved studies.     

A specific intramolecular interaction in a bis(2-thienyl)maleimide derivative

Russian Chemical Bulletin - 3,4-Bis(4-ethoxycarbonyl-3-hydroxy-5-methyl-2-thienyl)-1-phenyl-1H-pyrrole-2,5-dione shows no photochromism in the crystalline state, despite its typical...