FLUORIDE ΙΟΝ - MEDIATED REACTIONS OF DISUBSTITUTED ACETYLENES Me3SiC=CMMe3 (M = C, Si, Ge, Sn) WITH ALDEHYDES AND KETONES

Abstract

The CsF / 18-crown-6 mediated reactions of disubstituted acetylenes Me 3 SiC^CMMe 3 (M = C, Si, Ge, Sn) with carbonyl compounds in benzene were studied. In all cases the interaction proceeds with cleavage of the Si-C sp bond and can be considered as the addition of ethynylsilane to the carbonyl C=0 bond. The formation of bissiloxy derivatives was detected for acetylenes with M=Si and Sn. The cleavage of the Ge-C sp does not occur under the conditions used. Transmetallation of 1-trimethylsilyl-2-trimethylstannylacetylene was observed to give a mixture of symmetrical bissilyl-and bisstannylacetylenes with the following bis(trimethylsilyl)acetylene addition to the carbonyl compound, the bisstannyl analogue being inactive in CsF / 18-crown-6 mediated conditions. These processes open a simple way for the synthesis of new ethynylsubstituted derivatives of germanium and tin. 1 H NMR spectra were recorded on a Varian 200 Mercury spectrometer (200 MHz) using CDCI 3 as a solvent. Mass spectra were registered on a GC-MS HP 6890 (70 eV) apparatus. GC analysis was performed on a Chrom-5 instrument equipped with a flame-ionization detector using a glass column packed with 5% OV-101/Chromosorb W-HP (80-100 mesh, 1.2 m χ 3 mm). Carbonyl compounds 1-12 were purified by distillation in vacuo prior the use. Bis(trimethylsilyl)acetylene (Aldrich) was used without purification. 1-Trimethylsilyl-2trimethylgermylacetylene [11], 1-trimethylsilyl-2-trimethylstannylacetylene [11] and 1-tert-butyl-2trimethylsilylacetylene [12] were prepared according to the procedures described in [13,14]. CsF was calcinated at ca 200°C during 1 h. Benzene was distilled over CaH 2 and kept over molecular sieves 4A.General procedure for the synthesis of 13 -42. Freshly calcinated CsF (0.03 g, 0.2 mmol) was to a mixture of 1 -12 (1mmol) and 18-crown-6 (0.026 g, 0.1 mmol) in 1.5 ml of dry benzene under argon atmosphere added. After 5-minute stirring the corresponding acetylene (1 mmol) 243 Brought to you by | Purdue University Libraries

Alkynylxenon(II) Fluorides

“…In a similar manner as trimethyl(aryl)silanes, trimethyl(alkynyl)silanes, Me 3 SiC⋮CR, can be used as transfer reagents in fluoride substitutions . Reactions of trimethyl(alkynyl)silanes under fluoride ion initiation in organic synthesis were reported by Abele et al , The reactions of several trimethyl(alkynyl)silanes with xenon difluoride and tetramethylammonium fluoride in dichloromethane or a dichloromethane/propionitrile mixture were investigated at temperatures between −78 and −30 °C by multinuclear NMR spectroscopy (Scheme ).

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