Phase Transfer Catalysis Preparation of Acyl Isothiocyanates

The use of phase transfer catalysis, PTC, for nucleophillic substitution reactions is well documented.^1,2 Included among these reactions is the preparation of both alkyl³ and aryl⁴ thiocyanates. However, PTC reactions at an acyl carbon are much less common. Brándstróm⁵ has reported the preparation of acyl azides and Weber⁶ has used PTC to prepare benzoyl cyanide. Recently Illi⁷ has used PTC to acylate sterically crowded phenols.     

The Phase Transfer Catalysed Preparation of 2-Methyl-2-Trichloromethyl-3-Phenyloxirane

A phase transfer catalyst has been used to prepare the title compound and other highly chlorinated compounds from phenylpropanone and carbon tetrachloride.     

Rhodium-Catalyzed Addition of Aryl Boronic Acids to 2,2-Disubstituted Malononitriles

β-Ketonitriles bearing a quaternary carbon at the 2-position were prepared through Rh-catalyzed addition of aryl boronic acids to 2,2-disubstituted malononitriles. In contrast to the previously described transnitrilative cyanation of aryl boronic acids with dialkylmalononitriles, the present reaction avoids retro-Thorpe collapse of the intermediate addition product through the use of a milder base. The reaction was amenable to a variety of aryl boronic acids and disubstituted malononitriles, providing a diverse array of β-ketonitriles. The products could be further derivatized to valuable chiral α,α-disubstituted-β-aminonitriles through addition reactions to the corresponding N-tert-butanesulfinyl imines.     

General Synthetic Route to Monosubstituted Cycloheptadienes from Organometallic Compounds

An examination of the literature reveals that only a limited number of monosubstituted cycloheptadiene compounds have been reported. An obvious synthetic route to 5-substituted -1, 3-cycloheptadiene derivatives would be the reaction of nucleophiles with the cycloheptadienyl cation, but this pathway is generally unsuccessful due to the limited stability of the cation. On the other hand, the iron tricarbonyl complex of this cation shows remarkable stability¹ and an ability to react with nucleophiles². If the -Fe(CO)₃ group could be removed easily, a facile route to this family of organic compounds would be available. This work reports our investigation of the range of nucleophiles that can be utilized and the oxidizing agents that can remove efficiently the -Fe(CO)₃ group.     

Phase Transfer Catalysis Preparation of Arvl,Thiocyanates

Phase transfer catalvsis, PTC, has become a common preparative method in organic chemistry. Numerous aliphatic substitution reactions have been performed yielding cvanides,¹ azides,² thiocyanates,³ ethers,⁴ and many other types of substitution products.¹     

Virtual isotropic‐nematic transitions in alkyl cyanobiphenyls

Pretransitional fluctuations in the isotropic phase of liquid crystalline and non‐liquid crystalline alkyl cyanobiphenyls have been investigated using light scattering and magnetic birefringence measurements. We find evidence for a virtual isotropic‐nematic phase transition in short‐chain alkyl cyanobiphenyls with no observable nematic phase. The measured temperature dependence of fluctuations is well‐described by mean‐field theory. Virtual phase transition temperatures extrapolated from separate light scattering and magnetic birefringence experiments are in good agreement. Landau–de Gennes model parameters for the compounds investigated are calculated from the experimental results.     

Excitation of cladding modes in photonic crystal fibers by flexural acoustic waves

We report the excitation by flexural acoustic waves of an individual cladding mode in a single-mode photonic crystal fiber. The propagation constant and the field distributions of the mode have been investigated by use of this technique. The results give the basis for developing a family of acousto-optic devices based on photonic crystal fibers.     

Solutions of the kinetic theory for bounded collisional granular flows

We consider collisional granular flows of nearly elastic spheres featuring a single constituent or binary mixtures in various bounded geometries. We review the equations of the kinetic theory for the conservation of mass, momentum, fluctuation energy and species concentration. We illustrate their solutions for shear flows in rectilinear or axisymmetric rectangular channels with or without a body force. We show that proper boundary conditions yield numerical solutions in good agreement with molecular dynamical simulations and with data from physical experiments carried out in microgravity.Received: 3 December 2002, Accepted: 3 February 2003, Published online: 27 June 2003PACS: 45.70.Mg, 45.70.-n, 05.20.Dd, 83.10.Rs