Set the controls for the heart of the Sun

In this paper we describe experiments conducted with high-power lasers that are attempting to replicate, for a very short time and in miniature, conditions found in the Sun. Experiments to date have reached conditions in the outer part of the Sun. To reach the Sun's centre requires compression of material to very much greater than solid density and heating to over ten million degrees. To achieve this, a new class of experiments and a new generation of high-power lasers are required.     

Synthesis and Solid‐State,Solution, and Luminescence Properties of Near‐Infrared‐Emitting Neodymium(3+) Complexes Formed with Ligands Derived from Salophen

A series of free ligands, H₂ L ¹ , H₂ L ² , H₂ L ³ , and H₂ L ⁴ , designed for the coordination and sensitization of near‐infrared(NIR)‐emitting Nd³⁺ were synthesized by modifying the salophen Schiff base with different numbers and locations of Br‐substituents. The nature of the Nd³⁺ complexes in solution was determined to be [ML₂]^? by spectrophotometric titrations as an indication that the different substituents do not affect significantly the nature of the formed species. The structures were determined in the solid phase from X‐ray diffraction experiments. The stoichiometries and structures in the solid state are different from those observed in solution. We established that the structures in the solid state can be partially controlled by the crystallization conditions. The ligands L ¹ – L ⁴ have the ability to sensitize Nd³⁺ through intramolecular energy transfer from the ligand to the metal ion. We quantified that the numbers and locations of Br‐substituents control the emitted luminescence intensity of the complex by the heavy‐atom effect.     

Aerobic oxidation of tetrahydrofuran by a series of iron (III) containing POSS compounds

A series of iron (III) containing POSS compounds, [Bu₄N][(R)₇Si₇O₁₂FeCl] (R = isobutyl- (1), ethyl- (2), phenyl- (3), and cyclopentyl- (4)) were investigated as potential catalysts for aerobic oxidation of tetrahydrofuran (THF). The oxidation products for this reaction were characterized by IR, GC and GC–MS. The major oxidation product was γ-butyrolactone (C₄H₆O₂, GBL); while the two minor products were 2-hydroxy-THF and its tautomer, 4-hydroxybutanal. A third minor oxidative product is believed to be an isomer of dihydroxy-THF. THF free syntheses of 2–4 have been developed and all three compounds were characterized by elemental analysis, IR, and X-ray diffraction studies. The crystallographic data for 1–4 demonstrate a similar iron coordination sphere between the four compounds, but the different substitutents on the various POSS. The corresponding turnover numbers for the aerobic oxidation of THF suggest that smaller substitutents on the POSS ligands improve the stability of the catalytic species. When compared to other published catalytic iron systems, these turnover numbers appear to be the largest for the aerobic conversion of THF to GBL.     

Synthesis of fluorous and nonfluorous polycyclic systems by one-pot, double intramolecular 1,3-dipolar cycloaddition of azomethine ylides

[reaction: see text]. Under microwave irradiation, a one-pot, double intramolecular [3 + 2]-cycloaddition reaction of azomethine ylides leads to formation of a novel hexacyclic ring system. The major diastereomer is isolated, and its stereochemistry is determined by X-ray crystal structure analysis.     

An allenic Pauson-Khand-type reaction: a reversal in pi-bond selectivity and the formation of seven-membered rings

[reaction: see text] Treatment of alkynyl allenes with [Rh(CO)(2)Cl](2) results in a formal [2 + 2 + 1] cycloaddition reaction. This reaction occurs with complete regioselectivity for a variety of substrates affording only 4-alkylidene cyclopentenones in good yields. Moreover, seven-membered rings have been prepared in high yields.     

Exploring the substrate specificity of OxyB, a phenol coupling P450 enzyme involved in vancomycin biosynthesis

OxyB is a cytochrome P450 enzyme that catalyzes the first oxidative phenol coupling reaction during vancomycin biosynthesis. The preferred substrate is a linear peptide linked as a C-terminal thioester to a peptide carrier protein (PCP) domain of the glycopeptide antibiotic non-ribosomal peptide synthetase. Previous studies have shown that OxyB can efficiently oxidize a model hexapeptide-PCP conjugate (R-Leu(1)-R-Tyr(2)-S-Asn(3)-R-Hpg(4)-R-Hpg(5)-S-Tyr(6)-S-PCP) (Hpg = 4-hydroxyphenylglycine) into a macrocyclic product by phenolic coupling of the aromatic rings in residues-4 and -6. In this work, the substrate specificity of OxyB has been explored using a series of N-terminally truncated peptides related in sequence to this model hexapeptide-PCP conjugate. Deletion of one or three residues from the N-terminus afforded a penta- (Ac-Tyr-Asn-Hpg-Hpg-Tyr-S-PCP) and a tri- (Ac-Hpg-Hpg-Tyr-S-PCP) peptide that were also efficiently transformed into the corresponding macrocyclic cross-linked product by OxyB. The tripeptide, representing the core of the macrocycle in vancomycin created by OxyB, is thus sufficient, as a thioester with the PCP domain, for phenol coupling to occur. The related tetrapeptide-PCP thioester was not cyclized by OxyB, neither was a related model hexapeptide containing tryptophan in place of tyrosine-6, nor were tripeptides (related to the natural product K-13) with the sequence Ac-Tyr-Tyr-Tyr-S-PCP cross-linked by OxyB.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.