1-silyl-1-alkyne alkanal

Palladium catalysts, 230 of alkyl silyl ethers to alkanes Nickel boride, 197 of alkyl sulfonates to alkanes Lithium triethylborohydride, 153 of alkynes to cis-alkenes... 

Activation of two Si—Si bonds in bis(disilanyl)alkanes with palladium(O) bis(tert-alkyl isocyanide) induced the formation of the cyclic bis(silyl)palladium(II) bis(terf-alkyl isocyanide) complexes (100) and disilanes described schematically in Scheme 42. These complexes were found to react with phenylacetylene, affording different amounts of five-membered cyclic products and acyclic products which are derived from the insertion of the alkyne into the general intermediate complex 101 (Scheme 42, equation 54). The bis(silanyl)dithiane palladium complex (102) was isolated and characterized in the solid state the two silicon atoms, the two isocyano carbons and the palladium atom are nearly in a plane with a short cross-ring Si—Si distance of 2.613(2) A, suggesting the possibility of covalently bonded two Si—Si atoms in the four-membered ring. Similar reaction with cyclic disilanes afforded oligomers, and cyclic 20-membered compounds have been prepared in the presence of nitriles248,249. 

Alkynylsilanes—reactive precursors and versatile synthons for various reactions—can be obtained mainly by silylation techniques of metallated alkynes (including Grignard derivatives), or by elimination reactions of halogenated alkanes and alkenes in the presence of a silylating agent. The main classes of alkynylsilanes will be discussed as well as some derivatives which may be of further interest to organic synthesis. 

In contrast to the rare occurrence of the oxidative addition of C-C bonds, the oxidative addition of the nonpolar bonds between two main group atoms, such as boron and silicon, can be facile. The oxidative addition of Si-Si bonds in disilanes and the B-B bond in diborane(4) reagents is likely to be a step in a variety of catalytic reactions, including the additions of disilanes, - diborane(4) reagents, and silaboranes - across olefins and alkynes, the silylation and borylation of arene C-H bonds, - - the borylation of alkane C-H bonds, and the conversion of aryl halides to arylsilanes and arylbo-ronate esters. " ... 

The oxidative addition of disilanes occurs to palladium complexes of isonitrile ligands and platinum complexes of trialkylphosphine ligands as part of tiie catalytic silylation of alkynes and aryl halides. The addition of stannylboranes to Pd(0) complexes has also been reported,and the addition of diboron compounds to many metal systems, such as Pt(0) complexes (Equation 6.67), is now common. These reactions all occur with metal complexes that do not undergo intermolecular reactions with alkane C-H bonds, let alone C-C bonds. Thus, the Lewis acidic character of these reagents must accelerate the coordination of substrate and cleavage of the E-E bonds. 

As in hydroformylation, both linear and branched products can be obtained from RCH=CH2.The dehydrogenative silylation product, RCH=CHSiR3, is often present and can even predominate under some conditions (Eq. 9.21). The dehydrogenative path can only be explained on the modified Chalk-Harrod mechanism of Eq. 9.23, in which the alkene first inserts into the M-Si bond. 3 elimination of the intermediate alkyl now leads directly to the vinylsilane, the two H atoms thus released go on to hydrogenate the substrate leading to coproduction of alkane. As in hydrogenation, syn addition is generally observed. Apparent anti addition is due to isomerization of the intermediate metal vinyl, as we saw in Eq. 7.21, also a reaction in which initial insertion of alkyne into the M-Si bond must... 

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