A formal, metal-free, [2 + 2 + 2] cycloaddition strategy is described based on a cascade of two pericyclic processes. The first step involves an intramolecular propargylic ene reaction of a 1,6-diyne to generate a vinylallene, which then reacts in an inter-or intramolecular Diels-Alder reaction with an alkenyl or alkynyl dienophile. Reactions involving unsymmetrical alkenyl and alkynyl dienophiles proceed with good to excellent regioselectivity, and the diastereoselectivity in the Diels-Alder step is also high, with endo cycloadducts produced as the exclusive products of the reaction. In the case of alkynyl dienophiles, [4 + 2] cycloaddition initially generates an isotoluene-type intermediate that isomerizes to the isolated aromatic product upon exposure to a catalytic amount of DBU at room temperature. The mechanism of several earlier fully intramolecular related transformations have been shown to involve an analogous process rather than the diradical-mediated pathways proposed previously.

Stable conformations of 12-crown-O3N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O3N and its Li+ complex, our procedure was to make use of two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O3N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li+ changes depending on the distance between the cation and the crown ring.

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Lithium tantalate, LiTaO 3 (LT), single crystal growth by the vertical Bridgman (VB) technique is attempt for the first time. In the present VB-LT technique, pure platinum crucibles are used in a furnace with a graphite heater and an argon atmosphere. One-hundred percent solidified crack-free VB-LT crystals are successfully grown by composing the initial melts with exactly congruent compositions. The fundamental technical issues for VB-LT growth are also clarified.

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