Reduction of strained polycycles: how much strain can a pyrene anion take?

The reduction of a series of [n](2,7)pyrenophanes (n = 7-10) with lithium or potassium metal shows that the strain in the system, controlled by the length of the tether, determines the nature of the reduction products. The reduction of [7](2,7)pyrenophane (2) and [2]metacyclo[2](2,7)pyrenophane (3) leads to reductive dimerization followed by novel intramolecular sigma-bond formation as a means of escaping strained anti-aromaticity. [8](2,7)Pyrenophane (4) affords only reductive dimerization, and no two-electron reduction is observed. The reduction of [9](2,7) pyrenophane (5) and [10](2,7)pyrenophane (6) leads to reductive dimerization, followed by the formation of a dianionic anti-aromatic species, which eventually cleaves the solvent, THF-d(8). The similarity between the reduction of the latter systems and the reduction of pyrene (1) is discussed.     

"The great escape" from antiaromaticity: reduction of strained pyrenes

The two-electron reduction of strained pyrenes ([7](2,7)pyrenophanes) with lithium metal leads to the formation of a new sigma-bond as a means to "escape" strained antiaromaticity.     

4-Fluorinated L-lysine analogs as selective i-NOS inhibitors: methodology for introducing fluorine into the lysine side chain

In the literature, the introduction of fluorine into bioactive molecules has been known to enhance the biological activity relative to the parent molecule. Described in this article is the synthesis of 4R-fluoro-L-NIL (12) and 4,4-difluoro-L-NIL (23) as part of our iNOS program. Both 12 and 23 were found to be selective iNOS inhibitors as shown in Table 2 below. Secondarily, methodology to synthesize orthogonally protected 4-fluoro-L-lysine and 4,4-difluoro-L-lysine has been developed.     

All-optical regenerative memory for long term data storage

We describe a novel all-optical regenerative memory comprising two nonlinear optical switching gates coupled by an optical fibre storage loop. Binary pulse patterns were stored in the memory circuit for periods of several hours. This long term storage corresponds to > 10 billion circulations around the fibre storage loop.     

Intrinsic equations for a relaxed elastic line on an oriented surface

Hilbert and Cohn-Vossen [2, p. 221] incorrectly suggested a flexible knitting needle, constrained to conform to a surface, as one model for a geodesic on a surface. This model actually gives a relaxed elastic line on the surface, and is not generally a geodesic unless the surface lies in a plane or on a sphere.In this paper we derive the intrinsic equations for a relaxed elastic line on an oriented surface. This formulation should give a more direct and more geometric approach to questions concerning relaxed elastic lines on a surface. We apply this formulation to give alternate proofs of some results of [3] found by the less direct method of Lagrange multipliers and to give additional results about relaxed elastic lines on various surfaces. For further considerations of a relaxed elastic line on a surface as a model of the DNA molecule, see [3].Partially supported by NIH grant GM 36284-01.     

The reactions of [Co(η-C5H5)(CO)(L)] (L = R3P or RNC) with carbon disuphide and organoisothiocyanates

The reactions of [Co(η-C₅H₅)(CO)(PR₃)] or [Co(η-C₅GH₅)(CO)₂]/R₃P mixtures (R = alkyl or aryl) with CS₂ in refluxing CS₂ or CS₂/toluene gives rise to [Co(η-C₅H₅)(PR₃)(CS)], [Co(η-C₅H₅)(PR₃)(CS₂)], [Co(η-C₅H₅)(PR₃)(CS₃)], and [Co₃(η-C₅H₅)₃ (CS)(S)] in reasonable yields. The corresponding reactions using PhNCS give [Co(η-C₅H₅)(PPh₃)(PhNCS)] and a polymeric species which appears to be [Co₄(η-C₅H₅)₄ (PhNCS)]. Similar products are obtained with [Co(η-C₅H₅)(CO)(CNR)] or [Co(η0C₅H₅)(CO)₂]/RNC mixtures.     

Hydrogen abstraction by fluorine atoms under conditions of thermal initiation: Hydrocarbons and fluorinated hydrocarbons

Modified nuclear recoil techniques have been used to obtain accurate relative bimolecular rate coefficients for thermally induced hydrogen abstraction reactions by atomic fluorine. New results are reported for 12 hydrocarbons and partially fluorinated hydrocarbons studied at 303°K.     

Modelling,simulation, animation,and real-time control (MoSART) for a class of electromechanical systems: a system-theoretic approach

This paper describes an interactive modelling, simulation, animation, and real-time control (MoSART) environment for a class of ‘cart-pendulum’ electromechanical systems that may be used to enhance learning within differential equations and linear algebra classes. The environment is useful for conveying fundamental mathematical/systems concepts through computer-aided analysis, design, graphical visualization, and 3D animation. Referred to as Cart-Pendulum Control3D-Lab1Control3D-Lab-short for control 3D animation laboratory. The author to whom correspondence should be addressed., the environment is based on Microsoft Windows/Visual C++/Direct-3D and MATLAB/Simulink2MATLAB and Simulant are trademarks of The Masterworks, Inc.. Pull-down menus provide access to systems/models/control laws, exogenous signals, parameters, animation models and visual indicators, a suite of (easy-to-modify) Simulant diagrams containing models and control laws, MATLAB m-files for detailed analysis and design, and detailed documentation for each of the above. Three blocks enable animation, joystick inputs, and real-time animation within Simulant. Examples are presented to illustrate the utility of the environment as a valuable tool for analysing/visualizing the above class of electromechanical systems and for enhancing mathematics instruction.