Rhodium-catalyzed carbon-silicon bond activation for synthesis of benzosilole derivatives.

A rhodium-catalyzed coupling reaction of 2-trimethylsilylphenylboronic acid with internal alkynes is developed for the synthesis of 2,3-disubstituted benzosilole derivatives. A range of functional groups, encompassing ketones, esters, amines, aryl bromides, and heteroarenes, are compatible, which provides rapid access to diverse benzosiloles. Sequential 2-fold coupling enables modular synthesis of asymmetrically substituted 1,5-dihydro-1,5-disila-s-indacene, a π-extended molecule of interest in organic electronics. In terms of the mechanism, the reaction involves cleavage of a C(alkyl)-Si bond in a trialkylsilyl group, which normally requires extremely harsh conditions for activation. Mechanistic studies, including effects of substituents, reveal that C-Si bond cleavage does not proceed through a hypercoordinated silicon species, but rather through a rhodium-mediated activation process. The potential use of the reaction in catalytic asymmetric synthesis of Si-chiral benzosiloles is also demonstrated.

Rhodium-catalyzed coupling of 2-silylphenylboronic acids with alkynes leading to benzosiloles: catalytic cleavage of the carbon-silicon bond in trialkylsilyl groups.

The reaction of 2-(trimethylsilyl)phenylboronic acid with alkynes in the presence of a rhodium catalyst affords benzosilole derivatives. The arylvinylrhodium intermediate undergoes formal substitution at a silicon center, resulting in the cleavage of a robust silicon-methyl bond in the trimethylsilyl group.

Rhodium-catalysed anomalous dimerization of styrenes involving the cleavage of the ortho C-H bond.

The dimerization of styrene derivatives in the presence of a rhodium catalyst proceeds to give stilbene derivatives, in which the ortho C-H bond of styrenes is cleaved and functionalized.

[Kampo preparations for prostatic hyperplasia: usefulness of Saireito for nocturia].

Prostatic hyperplasia is characterized by major voiding symptoms, and treatment aims principally at improving the quality of life. Nocturnal frequency is a primary symptom that markedly impairs the quality of life. In addition to alpha 1-receptor blockers and antiandrogen agents, herbal medicines and kampo preparations have also been used, but they have not always proved satisfactory. In this study, we investigated the effect of a diuretic kampo preparation (Kanebo Saireito Extract Fine Granules) on urine output, and evaluated the efficacy of Saireito (5.4 g/day, bid) in 12 patients (mean age, about 68) with prostatic hyperplasia who had completed basic therapy but still complained of nocturnal frequency. The following results were obtained. 1) Saireito caused a significant increase of daytime urine output and significantly reduced nocturnal output. 2) It significantly reduced the nocturnal frequency, although that of daytime urination remained unchanged. 3) The drug significantly improved symptoms that existed before treatment. These results suggest that Saireito is effective for nocturia in patients with prostatic hyperplasia.