Alkynylsilanes and Alkynyl(vinyl)silanes. Synthesis,Molecular Structures and Multinuclear Magnetic Resonance Study

Abstract

Alkynylsilanes bearing one to four alkynyl groups at silicon, with organyl groups (Me, Ph, Vin), H, Cl at silicon, and with substituents H, n Bu, t Bu, Ph, C 6 H 4 -4-Me, 3-thienyl, CH 2 NMe 2 at the C≡C bond, were prepared, and their 13 C and 29 Si NMR data are reported. The results of X-ray structure analyses of three representative derivatives [di(phenylethynyl)dimethylsilane, di(phenylethynyl)methyl(phenyl)silane, and tri(phenylethynyl)methylsilane] are presented. The chemistry of mono-and dialkynylsilanes was further developed to prepare compounds with alternating Si atoms and C≡C bonds, affording new dialkynylsilanes as well as numerous new vinylsilanes which have also been characterized by 13 C and 29 Si NMR spectroscopy in solution. In the case of ethynyl(triphenylsilylethynyl)dimethylsilane, the molecular structure was determined by X-ray diffraction.

Synthesis and Characterization of Spirosilanes – 1,2‐Hydroboration and 1,1‐Carboboration

“…of the respective lithiated alkyne at low temperature (-78°C) [22][23][24] to afford the required dialkynyl(divinyl)silanes 1. For the tBu derivative, the reaction afforded a mixture of 1a and 2a (Scheme 1).…”

Combination of 1,2‐Hydroboration and 1,1‐Organoboration: A Convenient Route to 5‐Silaspiro[4,4]nona‐1,6‐diene Derivatives

“…[5][6][7] Recently, we characterized the first spirosilanes containing two four-membered rings B by using 1,2-hydroboration and 1,1-organoboration. [8] The combination of these stereo-and regioselective reactions is attractive in synthesis, [8][9][10] and in the present work further examples are given that are aimed at the synthesis and first structural characterization of the hitherto unknown 5-silaspiro[4,4]nona-1,6-diene derivatives.…”

Fused Silacarbacycles Containing a Silole Unit: 1,2‐Hydroboration and 1,1‐Organoboration of Alkynyl(vinyl)silanes

“…[15] In the course of the 1,2-hydroboration with 9-BBN, the vinyl group is preferred over the alkynyl group [Scheme 2 (a)]. In the next step, the neighbored Si-C(alkyne) bond is cleaved and 1,1-organoboration takes place [Scheme 2 (b); the intermediates shown in brackets indicate the mechanism of 1,1-orhganoboration [7] ].…”

“…The progress of the reactions is most conveniently monitored by 29 Si NMR spectroscopy, which, together with 13 C NMR spectroscopy, also serves to assign the structure of the final products. In the 29 Si NMR spectra, the signals typical of alkynylsilanes at low frequency [15,19,20] are replaced by 29 Si NMR signals at much higher frequencies, typical of the cyclic structures. [20] Particularly helpful for the structural as-signment is the observation of 29 Si satellites in the 29 Si NMR spectra, corresponding to the coupling constants 2 J( 29 Si, 29 Si) (see Figure 1), as well as in the 13 C NMR spectra, corresponding to n J( 29 Si, 13 C) (n = 1,2; see Figures 1 and 2).…”

“…The synthesis of the alkynylsilanes 1-5 is described elsewhere. [15] [26] and in some cases by gradient-enhanced 1 H-1 H NOE difference experiments. [27] EI-MS spectra: Finnigan MAT 8500 spectrometer (ionisation energy 70 eV) with direct inlet, the m/z data refer to the isotopes 1 H, 12 C, 11 B, 14 N, 28 Si.…”