Isoselenocarbonyl complexes.

The salt elimination reactions of [NEt4][Mo(CSe)(CO)2(Tp*)] ([NEt4][2], Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with a range of metal halide complexes (ClMLn) have been investigated as a possible route to isoselenocarbonyl complexes [Mo(CSeMLn)(CO)2(Tp*)]. Thus the reactions of [NEt4][2] with [RuCl(L)2(η-C5R5)] provide molybdenum-ruthenium derivatives [Mo{CSeRu(L)2(η-C5R5)}(CO)2(Tp*)] (L = PPh3, R = H 4, L = CO, R = Me 5), both of which were structurally characterised. The molybdenum-iron derivative [Mo{CSeFe(CO)2(η-C5H5)}(CO)2(Tp*)] (6) was obtained from [NEt4][2] and [FeCl(CO)2(η-C5H5)] however its formulation currently rests on spectroscopic and microanalytical data.

Highly selective catalytic -hydroboration of alkynes mediated by borenium cations and B(CF).

The -hydroboration of terminal alkynes mediated by borenium cations [NHC(9-BBN)] (NHC = N-heterocyclic carbene, 9-BBN = 9-borabicyclo(3.3.1)nonane) exclusively affords -vinylboranes.

Room temperature ring expansion of N-heterocyclic carbenes and B-B bond cleavage of diboron(4) compounds.

We report the isolation and detailed structural characterization, by solid-state and solution NMR spectroscopy, of the neutral mono- and bis-NHC adducts of bis(catecholato)diboron (B2 cat2 ). The bis-NHC adduct undergoes thermally induced rearrangement, forming a six-membered -B-C=N-C=C-N-heterocyclic ring via C-N bond cleavage and ring expansion of the NHC, whereas the mono-NHC adduct is stable. Bis(neopentylglycolato)diboron (B2 neop2 ) is much more reactive than B2 cat2 giving a ring expanded product at room temperature, demonstrating that ring expansion of NHCs can be a very facile process with significant implications for their use in catalysis.

syn-1,2-carboboration of alkynes with borenium cations.

The reaction of 8-(trimethylsiloxy)quinoline (QOTMS) with BCl3 and (aryl)BCl2 forms QOBCl2 and QOBCl(aryl). The subsequent addition of stoichiometric AlCl3 follows one of two paths, dependent on the steric demands of the QO ligand and the electrophilicity of the resulting borenium cation. The phenyl- and 5-hexylthienylborenium cations, QOBPh(+) and QOBTh(+), are formed, whereas QOBCl(+) is not.

Robust and Operationally Simple Synthesis of Poly(bis(2,2,2-trifluoroethoxy) phosphazene) with Controlled Molecular Weight, Low PDI, and High Conversion.

Synthetically straightforward conditions have been developed for the preparation of poly(bis 2,2,2-trifluoroethoxy)phosphazene with low PDI (<1.15) at high conversion (75-99%) and on a multigram scale. A combination of P NMR and GPC analyses demonstrate that molecular weight increases linearly as a function of monomer consumption, exhibiting first order kinetics with respect to monomer concentration up to high monomer conversion.

Haloboration of internal alkynes with boronium and borenium cations as a route to tetrasubstituted alkenes.

Hail boration! 2-Dimethylaminopyridine-ligated dihaloborocations [X2B(2-DMAP)](+) with a strained four-membered boracycle were used for the haloboration of terminal and dialkyl internal alkynes (see scheme). Esterification then provided vinyl boronate esters as useful precursors to tetrasubstituted alkenes. Following mechanistic studies, the scope of the haloboration was expanded simply by variation of the amine.

Mechanistic studies into amine-mediated electrophilic arene borylation and its application in MIDA boronate synthesis.

Direct electrophilic borylation using Y(2)BCl (Y(2) = Cl(2) or o-catecholato) with equimolar AlCl(3) and a tertiary amine has been applied to a wide range of arenes and heteroarenes. In situ functionalization of the ArBCl(2) products is possible with TMS(2)MIDA, to afford bench-stable and easily isolable MIDA-boronates in moderate to good yields. According to a combined experimental and computational study, the borylation of activated arenes at 20 °C proceeds through an S(E)Ar mechanism with borenium cations, [Y(2)B(amine)](+), the key electrophiles.

Reversible cyclopropane ring-cleavage reactions within etheno-bridged [4.3.1]propelladiene frameworks leading to aza- and oxa-[5.6.5.6]fenestratetraenes.

Opening and closing a chemical window: oxidation of the etheno-bridged [4.3.1]propelladienol 1 with pyridinium chlorochromate (PCC) affords oxa[5.

1-Borabenzonitrile (B-cyanoboratabenzene).

The reaction of 1-chloro-2-(trimethylsilyl)-1-boracyclohexa-2,5-diene with [(n)Bu(4)N]C≡N provides the 1-borabenzonitrile salt [(n)Bu(4)N][C(5)H(5)BC≡N] which in turn reacts with [Ru(4)(μ-Cl)(4)(η-C(5)Me(5))(4)] to afford the sandwich complex [Ru(η(6)-C(5)H(5)BC≡N)(η-C(5)Me(5))]. The bonding of 1-borabenzonitrile is discussed with recourse to crystallographic data for [(n)Bu(4)N][C(5)H(5)BC≡N] and [Ru(η(6)-C(5)H(5)BC≡N)(η-C(5)Me(5))].

Synthesis of the enantiomer of the structure assigned to the natural product nobilisitine A.

The synthesis of the enantiomer of the structure, 1, assigned to the natural product nobilisitine A has been accomplished using the enantiomerically pure cis-1,2-dihydrocatechol 4 as starting material. The (1)H and (13)C NMR spectral data derived from compound ent-1 do not match those reported for the natural product, thus suggesting its structure has been incorrectly assigned.

Metabolism of stanozolol: chemical synthesis and identification of a major canine urinary metabolite by liquid chromatography-electrospray ionisation ion trap mass spectrometry.

The canine phase I and phase II metabolism of the synthetic anabolic-androgenic steroid stanozolol was investigated following intramuscular injection into a male greyhound. The major phase I biotransformation was hydroxylation to give 6alpha-hydroxystanozolol which was excreted as a glucuronide conjugate and was identified by comparison with synthetically derived reference materials. An analytical procedure was developed for the detection of this stanozolol metabolite in canine urine using solid phase extraction, enzyme hydrolysis of glucuronide conjugates and analysis by positive ion electrospray ionisation ion trap LC-MS.

Asymmetric synthesis of bis(tertiary arsines): highly stereoselective alkylations of diastereomers of a chiral phosphine-stabilized bis(arsenium triflate).

The addition of organolithium reagents to an equilibrating mixture of diastereomers of a phosphine-stabilized 1,2-ethanediylbis(phenylarsenium triflate) containing chiral arsenic stereocenters and an enantiomerically pure, atropisomeric tertiary phosphepine derived from lithiated (aR)-2,2'-dimethyl-1,1'-binaphthalene generates unequal mixtures of diastereomers and enantiomers of chelating 1,2-ethanediylbis(tertiary arsines), chiral at arsenic, with liberation of the (aR(P))-phosphepine. Thus, the addition of methyllithium in diethyl ether at -95 degrees C to a dichloromethane solution of the complex (R*(As),R*(As))-(+/-)/(R*(As),S*(As))-1,2-[(R(3)P)PhAsCH(2)CH(2)AsPh(PR(3))](OTf)(2), where R(3)P is (aR(P))-[2-(methoxymethyl)phenyl]phosphepine, generates (R*(As),R*(As))-(+/-)-1,2-ethanediylbis(methylphenylarsine) in 78% diastereoselectivity and 95% enantioselectivity in favor of the (R(As),R(As)) enantiomer. Under similar conditions, the addition of n-butyllithium in hexanes to a solution of the bis(phosphepine-stabilized)-diarsenium triflate at -95 degrees C gives the corresponding (R*(As),R*(As))-(+/-)-1,2-ethanediylbis[(n-butyl)phenylarsine) in 77% diastereoselectivity and 93% enantioselectivity in favor of the (R(As),R(As)) enantiomer.