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An efficient and easy protocol for performing 1,3-dipolar cycloaddition using azomethine ylides and acrolein is presented. The reaction catalyzed by d-proline allows the synthesis of C-3 unsubstituted pyrrolidines. The application of this methodology to the synthesis of an advanced intermediate in the preparation of a Hepatitis C virus inhibitor is presented. Final attempts to complete the synthesis of the target inhibitor results in the preparation of its C-4 epimer in good overall yield

The objective of this program includes establishment of a generic method for the growth of single crystal films of important organic materials and measurement of their nonlinear optical properties. In the last three years we have developed a method which is a modification of the 'shear method' to prepare single crystal films of specific organic materials having very large second order nonlinearities. This is the first time that single crystal thin films of these organic materials have been prepared. The materials investigated include: (1) (N-(4-Nitrophenyl)-L-prolinol) (NPP), (2) (2-cyclooctylamino-5-nitropyridine), (COANP), (3) (8-(4'-acetylphenyl)-1,4-dioxa-8-azspiro4,5decane), (APDA) and (4) (4'-N,N-dimethylamino-4-N-methylstilbazolium toluene-p-sulfonate), (DAST). The single crystal films obtained for these materials have excellent optical quality and large areas (5 sq mm -2/sq cm depending on material). The films were characterized by x-ray diffraction, polarized FTIR, optical absorption and optical microscopy. The second order susceptibilities were measured and very large d-coefficients were observed. Electro-optic measurements have shown extremely large E-O coefficients. The off-resonant nonlinear refractive index of polydiacetylene was measured and picosecond all-optical switching at a high pulse repetition rate (82 MHz) was demonstrated for the first time.

Nonlinear optical (NLO) materials are an important component of many prospective Air Force applications including optical signal processing (switches, modulators, and guided-wave devices), and new laser sources (optical parametric oscillators and harmonic generators). Considerable progress has been made in the synthesis of frequency doubling (second harmonic generation - SHG) NLO chromophores and of polymeric materials containing such chromophores. A number of these SHG-NLO materials show noteworthy promise in small-scale characterizations. Commercialization of any of them requires that significant quantities of the materials, of demonstrable purity and stability, be readily available on a routine basis to these researchers who determine processing conditions as well as device manufactures.