Reaction of 1-trimethylsilylalkyne with copper(I) chloride in a polar solvent, DMF, at 60 degrees C under an aerobic conditions smoothly undergoes homo-coupling to give the corresponding symmetrical 1,3-butadiynes in 70-99% yields. In addition, (arylethynyl)trimethylsilanes are found to couple with aryl triflates and chlorides in the presence of Cu(I)/Pd(0) (10 mol %/5 or 10 mol %) cocatalyst system to give the corresponding diarylethynes in 49-99% yields. The cross-coupling reaction is applied to a one-pot synthesis of the corresponding unsymmetrical diarylethynes from (trimethylsilyl)ethyne via sequential Sonogashira-Hagihara and the present cross-coupling reactions using two different aryl triflates. The reactions of (arylethynyl)trimethylsilanes with aryl(chloro)ethynes in the presence of 10 mol % of CuCl also yield the corresponding unsymmetrical 1,3-butadiynes in 43-97% yields.

No abstract

The reaction of dimethyl(phenyl)silanol with butyl acrylate in the presence of a stoichiometric amount of Pd(OAc)2 or by a combined use of 0.1 molar amount of Pd(OAc)2 and Cu(OAc)2/LiOAc (molar ratio 3/2) gave butyl cinnamate in 76% or 57% yield, respectively. The similar reaction with tributyl(phenyl)tin also proceeded in 77% yield. The organotin compound was shown to react faster than the silanol, although the tin reagent sometimes induced undesirable homo-coupling, while the reaction with silanol did not give such by-product.

No abstract

Our studies on the constituents of Solanum-genera plants have resulted in the isolation of numerous steroidal glycosides: spirostane, furostane, solasodane and solanidane glycosides, some of which were found to exhibit anti-cancer 1) and anti-herpes simplex virus (HSV-1)2) activities. As a further extension of these studies, we began to investigate the constituents of Solanum cilistum, isolated six withanolidetype steroids which were different from the steroidal glycosides obtained to date from other Solanum plants and reported these in a preceding paper.3) In a continuing study on constituents of the leaves of the title plant, we have isolated additional six withanolide-type steroids. Herein we describe their structural characterization.A methanolic extract of the leaves (560 g) of this plant was extracted with hot MeOH repeatedly and evaporated under reduced pressure to give an extract (68.0 g) which was then treated with hexane. The insoluble layer was chromatographed on Diaion HP-20P by successively eluting with H 2 O, 30, 50, 70 and 90% aq. MeOH. The respective fractions were subsequently subjected to a variety of column chromatographies such as Chromatorex ODS (H 2 O→MeOH, gradiently), Sephadex LH-20 (MeOH) and silica gel (CHCl 3 -MeOHϭ20 : 1→10 : 1, CHCl 3 -MeOH-H 2 Oϭ9 : 2 : 0.1→8 : 2 : 0.2) to afford six whithanolide-type steroids, called cilistols v (1, 28.6 mg), t (2, 102.8 mg), i (3, 35.2 mg), j (4, 57.4 mg), y (5, 23.5 mg) and w (6, 344.5 mg).Cilistol v (1) was obtained as an amorphous powder, [a] D Ϫ23.4°(MeOH). A quasi-molecular ion peak at m/z 609 [MϩH] ϩ in the positive FAB-MS and elemental analysis of 1 indicated its molecular formula to be C 34 H 56 O 9 . The 1 H-NMR spectrum (in pyridine-