Jim Simpson

A limonoid from Xylocarpus granatum

A new limonoid, xyloccensin K, has been isolated from the seeds of Xylocarpus granatum, along with mixtures of steroids and long chain fatty acids and alcohols. X-ray crystallography has shown that xyloccensin K is similar to a number of previously reported limonoids, but that it contains a tetrahydrofuran sub-unit with oxygen bridging from C-3 to C-8.

Paramagnetic organometallic molecules : III. Photolysis of dimanganese decacarbonyl

Abstract The photolysis of Mn2(CO)10 has been investigated over a range of solvents and temperatures and found to be more complicated than hitherto reported. Homolysis of the metal—metal bond in Mn2(CO)10 is the dominant photochemical process in all solvents are evidenced by trapping the Mn(CO)5. radical. A temperature dependent bifunctionality of the spin-trap 2,4,6-tri-t-butylnitrosobenzene was observed. The unstable adduct Mn(CO)5O2., previously characterised in the solid state, is formed in non-polar solvents in the absence of a trap. A paramagnetic species giving rise to a broad, structureless signal at ambient temperatures is the major product in basic solvents; in certain polar solvents at low temperatures, hyperfine coupling to manganese (A(Mn) 88 G) could be distinguished. Both spectra are believed to derive from the solvated manganese(II) ion. The controversial six-line spectrum found on photolysis of Mn2(CO)10 in tetrahydrofuran also results from a manganese(II) species. The unusual properties of the Mn2(CO)10/THF system may be explained in terms of ion-pair formation between the Mn2+ and Mn(CO)5− ions in solution.

ELECTRONIC INTERACTIONS IN DIYNE CO2(CO)6 COMPLEXES

Abstract Electrochemical criteria are used to evaluate the electronic interaction between redox centres in the π-conjugated diyne complexes {RCC[Co 2 (CO) 6 ]CC[Co 2 (CO) 6 ]R} and {RCC[Co 2 (CO) 6 ](S)C[Co 2 (CO) 6 ]} (RPh, Fc) where the aromatic spacer S is phenyl, napthalene or anthracene. Voltammetry at microelectrode, differential pulse techniques and low temperature measurements are used to obviate the chemical complications following the primary redox process. A mechanism is proposed which successfully simulates the electrochemical data.

Polysilane derivatives of the transition metals ☆: IV. The crystal and molecular structures oftrimethylsilylpentacarbonylrhenium,me3sire(co)5, and[tris(trimethylsilyl)silyl] pentacarbonylrhenium, (me3si)3sire(co)5

Abstract The crystal and molecular structures of trimethylsilylpentacarbonylrhenium, Me3SiRe(CO)5, and [tris(trimethylsilyl)silyl]pentacarbonylrhenium, (Me3Si)3SiRe(CO)5 have been determined from three-dimensional X-ray data obtained by counter methods. Me3SiRe(CO)5 crystallises in space group P21/c of the monoclinic system with four molecules in a unit cell of dimensions: a = 6.972(4), b = 13.418(6), c = 13.400(5) A, β 91.85(5)°. The observed and calculated densities are 2.11 (±0.01) and 2.12 g cm−3 respectively. Block-diagonal least-squares refinement of the structure has led to a final value of the conventional R factor of 0.080 for the 1297 independent reflections having Fo2 > 3σ (Fo2). (Me3Si)3SiRe(CO)5 crystallises in the triclinic space group P 1 with two molecules in a unit cell of dimensions: a = 9.131(2), b = 9.358(2), c = 15.931(3) A, α 84.78(2), β 105.46(2), γ 111.99(2)°. The observed and calculated densities are 1.56 (±0.01) and 1.57 g cm−3 respectively. Block-diagonal least-squares refinement of the structure has led to a final value of the conventional R factor of 0.060 for the 1149 independent reflections having Fo2 > 3 σ (Fo2). For both structures, the coordination geometry about the rhenium atom is approximately octahedral, and, about the silicon atom bonded to the rhenium atom, tetrahedral. The relative orientations of carbonyl and methyl (or trimethylsilyl) groups, when viewed down the ReSi bond, appear consistent with minimisation of energy due to non-bonded interactions. In Me3SiRe(CO)5 all four of the equatorial carbonyl groups are displaced out of the equatorial plane towards the silicon ligand by about 5°.The SiRe bond is 2.600(1) A long. In (Me3Si)3SiRe(CO)5 only one of the equatorial carbonyl groups is displaced out of the equatorial plane towards the silicon ligand by 6 °. The SiRe bond is 2.665(9) A long.

Electron transfer in organometallic clusters: XI. Redox chemistry of M3(CO)12(M = Ru, Os) and PPh3 derivatives; mechanism of catalysed nucleophilic substitution

Abstract The generality of a two-electron reduction process involving an mechanism has been established for M3(CO)12 and M3(CO)12−n(PPh3)n (M = Ru, Os) clusters in all solvents. Detailed coulometric and spectral studies in CH2Cl2 provide strong evidence for the formation of an ‘opened’ M3(CO)122− species the triangulo radical anions M3(CO)12−· having a half-life of

Intramolecular interactions in 2,6-pyridylacetylenes and their Co2(CO)4dppm complexes

Abstract A series of 2,6-ethynylpyridyl compounds BrC5H3N(C2)R, C5H3N[(C2)R]2, BrC5H3N[RC2Co2(CO)4dppm], C5H3N{[R′C2Co2(CO)4dppm]C2R} and C5H3N[(R2C2Co2(CO)4dppm)]2 (R′=H, SiMe3, Fc), C5H3N(C2SiMe3)(C2R) R=H, Fc, {C5H3N(C2SiMe3)2} and {C5H3N[C2C5H3N(C2SiMe3)]2} have been prepared in order to study through-space and through-bond interactions between the ethynyl arms. The structure of BrC5H3N[FcC2Co2(CO)4dppm] shows that the Co2-alkyne unit is preferentially distorted, rather than the ethynyl arms bent, in order to minimise steric interactions. Although, there is no evidence for through-bond or through-space electronic communication between the redox centres, intramolecular interactions force a η2(dppm)–η1(dppm) equilibrium upon the oxidised Co2(CO)4dppm unit, which is seen in the electrochemistry and OTTLE data.

Polysilane derivatives of the transition metals III. Preparations and spectra of manganese and iron derivatives

Abstract The preparations of derivatives of Mn(CO) 5 , Mn(CO) 4 PPh 3 and π-Cp(CO) 2 Fe containing the polysilyl ligands (Me 3 Si) n Me 3− n Si— ( n = 1–3) are presented. The infrared and proton NMR spectra of the compounds are given and for the Mn(CO) 5 derivatives, force constants are derived and discussed in terms of the σ-donor/π-acceptor properties of the silyl ligands.

Toxicology and antitumour activity of ferrocenylamines and platinum derivatives

Toxicity, antitumour, platinum distribution, hepatotoxicity and histology data are presented for a series of ferrocenylamines: [(η-C 5 H 4 (CH 2 ) n NH 2 )FeCp] (n = 0,1) (1,2); [(η-C 5 H 4 CH 2 NHPh)FeCp] (3); [(η-C 5 H 4 CH 2 NMe 2 )FeCp (4); {[η-C 5 H 4 CH(Me)NMe 2 ]FeCp}(5); [η-C 5 H 4 CH 2 NMe 2 ) 2 Fe](6); {[1,2η-C 5 H 3 (CHMeNMe 2 )(PPh 2 )] FeCp}(7); {[1,2η-C 5 H 3 (CHMeNMe2)(PPh 2 )]-Fe[η-C 5 H 4 PPh 2 ]}(8); and their complexes cis-PtCl 2 L 2 (9); trans - Pt(L)(dmso)X 2 (10); [σ -(L)Pt(dmso)X] (11,12) {σ-(L)[Pt(dmso)X] 2 } (13); [σ-(L)PtP(OPh) 3 Cl] (14) (L = ferrocenylamine). The toxicity order is 1-3 » 4-8 for the ferrocenylamines; the lower toxicity of tertiary amines may be due to protonation in vivo. Pt(II) complexes all show increased toxicity over the ligand. Liver, not kidney, damage is the norm from i.p. injection of 1-14 and detailed platinum distribution, blood serum and histology studies with 9 and 11 show that the platinum distribution does not correlate with liver dysfunction. Complexes 9-14, but not 1-8, were active against P-388 mouse leukaemia tumour and cisplatin-resistant sarcoma, but inactive against L-1210 mouse leukaemia and B-16 melanoma.

Synthesis of the 6-Azaindole Containing HIV-1 Attachment Inhibitor Pro-Drug, BMS-663068

The development of a short and efficient synthesis of a complex 6-azaindole, BMS-663068, is described. Construction of the 6-azaindole core is quickly accomplished starting from a simple pyrrole, via a regioselective Friedel-Crafts acylation, Pictet-Spengler cyclization, and a radical-mediated aromatization. The synthesis leverages an unusual heterocyclic N-oxide α-bromination to functionalize a critical C-H bond, enabling a highly regioselective copper-mediated Ullmann-Goldberg-Buchwald coupling to install a challenging triazole substituent. This strategy resulted in an efficient 11 step linear synthesis of this complex clinical candidate.

A monoclinic polymorph of N-(3-chloro­phen­yl)benzamide

The title compound, C13H10ClNO, (I), is a polymorph of the structure, (II), first reported by Gowda et al. [Acta Cryst. (2008), E64, o462]. In the original report, the compound crystallized in the orthorhombic space group Pbca (Z = 8), whereas the structure reported here is monoclinic P21/c (Z = 4). The principal difference between the two forms lies in the relative orientations of the phenyl and benzene rings [dihedral angle = 8.90 (13)° for (I) and 61.0 (1)° for (II)]. The inclination of the amide –CONH– units to the benzoyl ring is more similar [15.8 (7)° for (I) and 18.2 (2)° for (II)]. In both forms, the N—H bonds are anti to the 3-chloro substituents of the aniline rings. In the crystal, intermolecular N—H⋯O hydrogen bonds form C(4) chains along c. These chains are bolstered by weak C—H⋯O interactions that generate R 2 1(6) and R 2 1(7) ring motifs.