Transmetallation: A highly regio- and diastereoselective carbocyclization involving a palladium-catalyzed 1,2-addition of two carbon atoms across a conjugated diene has been developed (see scheme). The reaction is performed with dienynes and an oxygen tether containing a terminal or internal triple bond.

Reaction of (N(3)N)ZrPHPh (N(3)N=N(CH(2)CH(2)NSiMe(3))(3)(3-)) with PhCH(2)N[triple bond]C affords the 1,1-insertion product (N(3)N)Zr[C(PHPh)=NCH(2)Ph], which thermally rearranges to the phosphaalkene-containing complex, (N(3)N)Zr[N(CH(2)Ph)C(H)=PPh].

The title compound, C(26)H(24)N(2)O(4), consists of a symmetrical mol-ecule that lies across a crystallographic inversion centre. The C-C distance in the triple bond is 1.188 (2) Å and there is also an inter-molecular C-H⋯O contact from a terminal acetyl-ene C-H to one of the dimiide O atoms [3.4349 (19) Å].

Zirconacyclopropenylboronates can be stabilized to dimerization by complexation with tributylphosphine; the phosphine stabilized zirconacycle boronates react with aliphatic and aromatic ketones and aldehydes at C2 of the triple bond to give the previously unknown 3-hydroxyvinylboronates in 61-80% isolated yields.

Beta-solenoids are a class of protein nanotube structures that are observed in virulence factors, prion proteins and amyloid fibrils. Here we investigate the compressive strength of the triple-beta-helix solenoid structure found in the cell puncture needle of the bacteriophage T4 virus. We characterize the compressive mechanical strength of this protein nanotube using full-atomistic molecular d...

The first crystallographic and electron density distribution analyses of a thioaroyl cation unveil its true structural perspective; this chemical species can be mainly expressed as the combination of the thioketene form (II) and sulfonium form (III) with a C≡S(+) triple bond character.

Conformational analysis of modeled cis-unsaturated chains in triunsaturated and symmetrical monounsaturated triglycerides has identified pseudo-linear chain orientations that allow lower molecular mechanical energies than are possible with conventional cis-chains. Energy plots recorded during bond rotations near the double bond show that energy barriers between linear and normal cis-configurati...

Ab initio calculations are presented for several species containing a silicon-phosphorus bond. The types of bonding studied include "normal" single, double, and triple bonds, as well as an ylide-like structure. The latter is found to be much less strongly bound than the carbon analogue, with a smaller stretching force constant than that in silylphosphine. The insertions of silylene into the pho...

Theoretical description (MP2/6-311G* and B3LYP/6-311G*) is presented for hypovalent titanium alkoxide model compounds showing linear angleTi-O-C angles. This feature is explained by the existence of a polarized triple Ti-O bond. In contrast, a series of 18 electron germanium derivatives displaying bent angleGe-O-C angles contain polarized single Ge-O bonds. The nature of the Ti-O and Ge-O bonds...

The structures of cyanogen and diacetylene have been previously investigated by the electron-diffraction method by Wierl,I who reported nonlinear models with 1500 bond angles for both molecules. The improbability of this conclusion, which is incompatible with all other evidence for the angle between a triple and a single bond on the same carbon atom, led to a reinvestigation of these compounds ...