Fully Chlorinated N-Silyl Amides of Titanium and Tungsten

The reaction of hexachlorodisilazanyllithium (Cl3Si)2NLi (1), with TiCl4 leads selectively to the novel fully chlorinated amides (Cl3Si)2NTiCl3 (2) or [(Cl3Si)2N]2 TiCl2 (3), respectively, depending on the molar ratio of the starting materials. The analogous reaction of 1 with WCl6 yielded the amide imide Cl3SiNW(Cl3)N(SiCl3)2 (5) by elimination of SiCl4. The relative amounts of the starting materials had no effect on the formation of 5. 14/15N- and 29Si-NMR data on the starting materials and products show significantly different effects, when compared with those of analogous N-trimethylsilyl derivatives, due to the lower energy of the electrons in the NSi and NM ß bonds. The crystal structure of 5 (triclinic, space group P1) was determined by X-ray structure analysis

Syntheses of combretastatins D-1, D-2, and D-4 via ring contraction by flash vacuum pyrolysis

We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2.PostprintPeer reviewe

Ferrocenyl-coupled n-heterocyclic carbene complexes of gold(i): a successful approach to multinuclear anticancer drugs

Four gold(I) carbene complexes featuring 4-ferrocenyl substituted imidazol-2-ylidene ligands were investigated for antiproliferative and antivascular properties. They were active against a panel of seven cancer cell lines, including multidrug-resistant ones, with low micromolar or nanomolar IC50 (72 h) values, according to their lipophilicity and cellular uptake. The delocalised lipophilic cationic complexes 8 and 10 acted by increasing the reactive oxygen species in two ways: via a genuine ferrocene effect and by inhibiting the thioredoxin reductase. Both complexes gave rise to a reorganization of the F-actin cytoskeleton in endothelial and melanoma cells, associated with a G1 phase cell cycle arrest and a retarded cell migration. They proved antiangiogenic in tube formation assays with endothelial cells and vascular-disruptive on real blood vessels in the chorioallantoic membrane of chicken eggs. Biscarbene complex 10 was also tolerated well by mice where it led to a volume reduction of xenograft tumors by up to 80%