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A soluble and stable one-handed helical poly(substituted phenylacetylene) without the coexistence of any other chiral moieties was successfully synthesized by asymmetric-induced polymerization of a chiral monomer followed by two-step polymer reactions in membrane state: (1) removing the chiral groups (desubstitution); and (2) introduction of achiral long alkyl groups at the same position as the desubstitution to enhance the solubility of the resulting one-handed helical polymer (resubstitution). The starting chiral monomer should have four characteristic substituents: (i) a chiral group bonded to an easily hydrolyzed spacer group; (ii) two hydroxyl groups; (iii) a long rigid hydrophobic spacer between the chiral group and the polymerizing group; (iv) a long achiral group near the chiral group. As spacer group a carbonate ester was selected. The two hydroxyl groups formed intramolecular hydrogen bonds stabilizing a one-handed helical structure in solution before and after the two-step polymer reactions in membrane state. The rigid long hydrophobic spacer, a phenylethynylphenyl group, enhanced the solubility of the starting polymer, and realized effective chiral induction from the chiral side groups to the main chain in the asymmetric-induced polymerization. The long alkyl group near the chiral group avoided shrinkage of the membrane and kept the reactivity of resubstitution in membrane state after removing the chiral groups. The g value (g = ([θ]/3,300)/ε) for the CD signal assigned to the main chain in the obtained final polymer was almost the same as that of the starting polymer in spite of the absence of any other chiral moieties. Moreover, since the one-handed helical structure was maintained by the intramolecular hydrogen bonds in a solution, direct observation of the one-handed helicity of the final homopolymer has been realized in CD for the solution for the first time.

The intramolecular dehydrogenative cyclization of 2-(dialkylsilyl) biaryls proceeded in the presence of a catalytic amount of platinum(II) chloride and potassium tris(3,5-dimethyl-1- pyrazolyl)borohydride to give good yields of the corresponding dibenzosilole derivatives. [ABSTRACT FROM AUTHOR]

Highly selective photocyclic aromatization (SCAT) of poly(substituted acetylene)s, which can quantitatively yield the corresponding 1,3,5-trisubstituted benzene derivative, was applied to quantitative determination of the microstructures of copoly(substituted acetylene)s. By GPC analysisof the SCAT products of the copolymers of two substituted acetylenes having substituents whose molecular weights were greatly different, some clear information regarding the microstructures, such as sequence (triad) distribution and composition, which could not be obtained from NMR because of their broad peaks, could be obtained successfully under a mild condition. [ABSTRACT FROM AUTHOR]

An amphiphilic 1,3,5-trisubstituted benzene as a new 2D surface modifier (T-EO) which has six hydroxy groups and three oligoethylene groups was successfully and easily synthesized by selective photocyclic aromatization in high conversion and selectivity for the first time. We prepared four kinds of blend membranes based on PVA or poly(trimethylsilylphenylacetylene) (poly(SPA)) containing the new amphiphilic cyclic trimer (T-EO) or the corresponding polymer (P-EO), that is, T-EO/PVA, P-EO/PVA, and T-EO/poly(SPA) membranes prepared by conventional solvent casting method (Method I) and T-EO/poly(SPA) membranes prepared by a new solvent casting method (Method II). T-EO/PVA membranes by Method I and T-EO/poly(SPA) membranes by Method II showed better performance in oxygen permeation than P-EO/PVA membranes by Method I and T-EO/poly(SPA) membranes by Method I, respectively. A PVA-based membrane containing 1.0 wt% T-EO showed the best performance, that is, the α became twice that of the original PVA membrane without any decrease in PO2. The ideal improvement may be caused by effective surface modification by T-EO. [ABSTRACT FROM AUTHOR]

The intermolecular dehydrogenative coupling of 1,1,1,3,5,5,5-heptamethyltrisiloxane with aromatic compounds such as aryloxazolines and arylimines in the presence of a catalytic amount of [RuCl2 (p-cymene)] 2 gave the corresponding orthosilylated products in good yields. [ABSTRACT FROM AUTHOR]

A new polymer prepared by polymerization of 3,5-bis-(hydroxymethyl)phenylacetylene having a chiral menthyl group via a very long and rigid spacer by an achiral rhodium complex with triethylamine as an initiator showed strong CD absorptions assigned to the main chain in spite of the long distance (23¡) between the chiral group and the polymerizing group in the monomer. This distance is the longest to the best of our knowledge. In addition, switching between the two chiralities of the resulting polymer was realized in the CD spectrum. [ABSTRACT FROM AUTHOR]