Acylsilane complexes

A convenient route to both saturated and unsaturated acylsilanes lies in the hydroboration-oxidation of alkynylsilanes (Chapter 7). Recent improvements (6) to this method involve the use of the borane-dimethyl sulphide complex for hydroboration, and of anhydrous trimethylamine A-oxide for the oxidation of the intermediate vinyl boranes. 

Acyclic cationic systems, chalcogen-halogen compounds, 35 299-301 Acylarsonic acids, 44 217 Acyldiazenido complexes, mechanisms of formation, 27 223-225 Acylium cation, 9 231, 241-243 Acylphosphonic acids, 44 217 Acylsilane, hydrolysis, 42 173 Adamantane... 

When iridium complexes, [IrCl(CO)3]n and Ir4(CO)12, are used to catalyze the reaction of terminal alkenes with HSiR3 and CO, good yields of enol silyl ethers of acylsilanes are obtained. One molecule of CO and two molecules of silane are incorporated regioselectively at the terminal carbon atom of the alkene to form a siloxy(silyl)methylene unit [Eq. (38)].107... 

The steric bulk of the silyl groups in acylsilanes influences their asymmetric reduction to give chiral secondary alcohols by borane complexed with )-2-amino-3-... 

Silenes of the family Me3SiR1Si=C(OSiMe3)Ad-l 137 undergo a complex silene-to-silene photoisomerization reaction90,94,96. When silenes 137 are generated by photolysis of acylsilanes 138, the isomeric silenes 139 and 140 are formed in a subsequent reaction. The reaction was followed by UV and NMR spectroscopy. The disappearance of 138 cleanly follows first-order kinetics and the overall kinetics were consistent with the transformation 138 -> 137 -> 139. 137 as well as 139 were characterized by NMR spectroscopy and, in addition, the structure of 137 was established by trapping with methanol. The identity of 139 and 140 was confirmed by the isolation of their head-to-tail dimers from which crystals, suitable for X-ray analyses, were isolated (equation 34)90. 

Acyl(phosphido) complexes, with Pt(II), 8, 458 Acyl radicals, via selenium precursors, 9, 477 Acylsilanes, applications, 9, 319 Acylstannanes, preparation, 3, 822-823 l-Adamantyl-2-pyridyl amido complexes, with Zr(IV), 4, 782 Adaptive quantum control, for selective bond cleavage, 1, 247 Addition reactions... 

Hydrosilane HSiR.3 behaves similar to H2 toward transition metal complexes in some cases. When HSiR.3 is used instead of hydrogen in hydroformylation, two reactions are expected. One is a hydrocarbonylation-type reaction, by which formation of the silyl enol ethers 62 via the acylmetal intermediate 61, and the acylsilanes 64 via the acyl complex 63, are expected in practice both reactions are observed. The other possibility is silylformylation to form 65, which is unknown, even though silylformylation of alkynes is known. When Co2(CO)8 is used, the silyl enol ether of aldehyde 66 is obtained [36], However, the silyl enol ether 67 of acylsilane 68 is obtained when an Ir complex is used, and converted to the acylsilane 68 by hydrolysis [37],... 

Two simple a, P-unsaturated acylsilanes, l-trimethylsilyl-2-propen-l-one (III) and l-trimethylsilyl-2-methyl-2-propen-l-one (IV) were chosen for polymerization studies. The polymerization of the carbon analogues of these a,p-unsaturated acylsilanes, that is, 4,4-dimethyl-2-propen-3-one (vinyl tert-butyl ketone, V) and 2,4,4-trimethyl-2-propen-3-one (isopropenyl tert-hutyl ketone, VI) has been studied by Willson et al. 16, IT), These authors reported that whereas V readily polymerizes under free-radical-polymerization conditions, VI undergoes polymerization only under anionic-initiation conditions in the presence of a crown ether as a complexing reagent. On the basis of UV and NMR spectroscopic data, Willson et al. (i6, 17) ascribed the difference in polymerization behavior to the nonplanar, unconjugated structure of ketone VI brought about by steric hindrance caused by the methyl group at C-2. 

The vinyl moiety can carry one, two, or three further substituents. Whereas the presence of a single substituent at the -carbon is relatively unusual [13,14], cases in which this substituent is at the /3-carbon (normally E-geometry, but see [17]) are much more common. This substituent can be simple [15] or more complex [16], and can itself bear functional groups such as OH [17,18], OEt [19], or NHj [20]. Ketal groups [21] or even an acylsilane residue (Scheme 4-2) [22] are tolerated. 

Acylsilanes may be prepared directly from either acyl chlorides or anhydrides by treatment with tris(trimethylsilyl)aluminum-ate complexes (equation 24). ... 

Preparation of acylsilanes via silyl-substituted organoaluminum-ate complexes... 

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