Silylated alkynes

FITS reagents), has undergone considerable development recently [141,142,143, 144, 14S. These compounds, available fromperfluoroalkyhodides (equation 76), are very effective electrophilicperfluoroalkylating agents They react with carban-lons, aromatic compounds, alkenes, alkynes, silyl enol ethers, and other nucleophiles under mild conditions to introduce the perfluoroalkyl moiety mto organic substrates (equation 77) (see the section on alkylation, page 446). 

Rhodium complexes catalyze hydrosilylation-cyclization of 1,6-allenynes in the presence of (MeO SiH.77 To avoid complex product distributions, the use of substrates possessing fully substituted alkyne and allene termini is imperative. As shown in the cyclization of 1,6-allenyne 62a, the regiochemistry of silane incorporation differs from that observed in the rhodium-catalyzed hydrosilylation-cyclization of 1,6-enynes (see Section 10.10.2.3.2). For allenyne substrates, allene silylation occurs in preference to alkyne silylation (Scheme 40). 

Tandem Reductive Alkyne Silylation/C-C Bond Formation 809... 

In common with ordinary alkynes, silylated alkynes are nucleophilic towards electrophiles. The presence of the silicon has a dramatic effect on the regioselectivity of this reaction attack occurs only at the atom directly bonded to the silicon. This must be because the intermediate cation is stabilized. 

AMition of l-alkynes to carbonylsJ Alkali metal acetylides are usually used for this addition, but their strong basic properties can cause problems with base-sensitive substrates. 1-Alkynes can add directly if the reaction is carried out in combination with Sn(OTf)2 and a base (1 1). In reactions with aromatic alkynes, DBU is the preferred base, but l,8-bis(dimethylamino)naphthalne is preferred for reactions with aliphatic alkynes. Silylation of l-alkynes with RsSiCI can also be promoted by Sn(OTf)2 and an amine. 

Halogenpyridines (or triflates) + terminal alkynes (silylated alkynes)... 

Although for the catalytic transformations of organosilicon compounds only hydrosilylation is well known as industrially important process, in the last 20 years other reactions of silicon compounds catalyzed by transition metal complexes have been discovered and developed. They include double (bis)silylation of alkenes and alkynes, silylative coupling of alkenes and alkynes with vinylsi-lanes, dehydrocoupling of hydrosilanes, silylformylation and silylcarbonylation of unsaturated compounds, and dehydrogenative silylation of alkenes and alkynes with hydrosilanes. Only the latter, as related to hydrosilylation (and very often its side reaction), has been discussed here (13). 

Details on oxidation and reduction reactions mediated by [(NHC)Pd] complexes can be found in Chapters 12 and 13, respectively. Further reports of interest disclosed include diboration of alkenes catalysed by a pincer complex, deuteration of C-H bonds with an N,0-functionalised NHC complex, and an intriguing Suzuki-type reaction of [FeI(Cp)(CO)2] with arylboronic acids. A number of useful C-heteroatom coupling reactions have also been reported recently, including alkene hydrophosphination and alkyne silylation. ... 

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