3- -2-siloxyallyl

These reagents are also useful for the preparation of 1,2-diols. Upon exposure to Lewis acids such as boron trifluoride etherate (BFa-OEta), the a-alkoxy and oc-siloxyallyl stannanes undergo a stereospecific, intermolecular 1,3-isomerization to give y-alkoxy- and y-siloxy allylic stannanes.3. .7 When tert-butyldimethylsilyl trifluoromethanesulfonate is substituted for chloromethyl methyl ether in the above procedure, the isomeric -y-siloxy allylic stannane can be obtained directly with no loss of enantioselectivity.6 These stannanes can then be added to various aldehydes to give monoprotected 1,2-diols with high diastereoselectivity.8... 

Siloxyallyl)silane 24, acting as a synthetic equivalent of acetone a,a -dianion, readily undergoes double alkylation (equation 15)60. An acid-catalyzed transacetalization-ring closure reaction occurs in the reaction of 6-hydroxy substituted allylsilanes 25 with acetals to afford the corresponding trisubstituted tetrahydropyrans in moderate to good yield with high diastereoselectivity (equation 16)61. 

Allyl cyanides can be added across alkynes in the presence of a nickel catalyst prepared from (COD)2Ni and (4-CF3CeH4)3P in situ to give functionalized di- or tri-substituted acrylonitriles in a highly stereoselective manner, presumably via n-allylnickel intermediates. a-Siloxyallyl cyanides also react at the y -position of a cyano group with both internal and terminal alkynes to give silyl enol ethers, which can be converted into the corresponding aldehydes or ketones upon hydrolysis.70... 

Under the catalytic action of palladium(O) complexes, (2-siloxyallyl) acetates and the vinylogous [4-(trimethylsiloxy)penta-2,4-dienyl] acetate (Table 18), (2-oxo-3-silylpropyl) acetates (1-acetoxy-3-silylpropan-2-ones), ° and (2-oxoalkyl) carbonates react with the strained, but otherwise nonactivated double bonds in norbornene, norbornadiene, and dicyclopentadiene to form polycyclic cyclopropyl ketones, see also formation of 1, 2 °and 3. In contrast, the (2-siloxyallyl) acetates failed to react with simple alkenes such as dec-1-ene and cyclohexene. " With the substrates mentioned, the exo anti) diastereomers were obtained exclusively. 

Cyclopropanation of Norbornene and Related Systems with (2-Siloxyallyl) Acetates Catalyzed by Pallad-ium(O) General Procedure ... 

Siloxyallyl)silanes such as 28, which contain both siloxy enol ether and allylsilane moieties, were suggested recently as suitable a,a -dianion synthons which, in the presence of a Lewis acid (TiCU, BF3-etherate), react with two molecules of an acetal 2 to give a corresponding double aldol type product 29 [30] (Scheme 5). 

Oxidative amination of aromatic amines which are less basic than aliphatic amines proceeds smoothly without protection of amines. The intramolecular reaction of aniline derivatives offers good synthetic methods for heterocycles. 2-Methylindole is obtained by 5-exo amination of 2-allylaniline [50]. As an application, A-methyl-2-methyl-3-siloxyindole 114 was prepared from A-methyl-2-(l-siloxyallyl)aniline 113. Without silyl protection, no reaction occurred [51]. If there is another olefinic bond in the same molecule, the aminopalladation product 116 of the amide 115 undergoes olefin insertion to give the tricyclic compound 117 [50]. 2,2-Dimethyl-1,2-dihydroquinoline (119) was obtained by 6-endo cyclization of 2-(3,3-dimethylallyl)aniline (118). 

Silyl enol ethers are shown to have nucleophilicity between that of allylsilanes and aliylstannanes, and siloxyallyl barium reagents couple RCHO and RX at the y-position. ... 

Chirality transfer from an a-silylalcohol to a-carbamoyloxy- and a-siloxyallyl-carbanions has been investigated using a Brook rearrangement-mediated 5 2 protonation in y-carbamoyloxy- and y-siloxy-ct-silylallyl alcohols. A reaction mechanism that proceeds along one of two pathways that involves a concerted protonation of a silicate intermediate and a concerted lithiation of the intermediate followed by protonation with retention or by protonation after racemization has been proposed. 

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