Chlorides allylsilane reactions with aldehydes

Optically active (Z)-l-substituted-2-alkenylsilanes are also available by asymmetric cross coupling, and similarly react with aldehydes in the presence of titanium(IV) chloride by an SE process in which the electrophile attacks the allylsilane double bond unit with respect to the leaving silyl group to form ( )-s)vr-products. However the enantiomeric excesses of these (Z)-allylsilanes tend to be lower than those of their ( )-isomers, and their reactions with aldehydes tend to be less stereoselective with more of the (E)-anti products being obtained74. 

Asymmetric hydrosilylation of 1,3-dienes provides convenient access to optically active a-chiral allylsilanes.107 1073 1071 The combination of 7r-allylpalladium chloride dimer with axially chiral monophosphine ligand 17 realizes high catalytic activity and enantioselectivity in the reaction of cyclic 1,3-dienes with HSiCl3.108,108a The allyltrichlorosilanes obtained react with aldehydes in a syn-Se mode to give homoallyl alcohols with high diastereo-and enantioselectivity (Scheme 9). 

Cyclopentene derivatives. These compounds are formed by reaction of 1 in the presence of TiCU with aldehydes, ketones, -keto esters, or o(, 8-unsaturated ketones. The allylsilane reacts with acyl chlorides in the presence of AICI3 to form cyclopentene-2-yl ketones, which are rearranged on silica gel to the a,/S-unsaturated ketones. ... 

Hydrozirconation and Zirconium-catalyzed Carboalumina-tion. Hydrozirconation of 3-trimethylsilyl-l-propyne using Schwartz s reagent gives the alfcenylzirconocene that can be further reacted to provide 1,3-dienes after Lewis-acid-catalyzed addition to aldehydes (eq 35), vinyl sulfones from reaction with sulfonyl chlorides (eq 36), and allylsilanes upon transmetalla-tion with CuBr followed by 1,4-addition (eq 37)." ... 

Selective Electrophilic Addition Reactions. The difference in reactivity between the allylstannane and aUylsilane functionalities incorporated within this bismetaUoid allows for selective reaction with electrophiles (eq 1). The more nucleophilic allylstannane moiety reacts preferentially with electrophiles such as acid chlorides and aldehydes under thermal conditions, thereby providing functionalized allylsilanes (eq 2). Related processes have been induced photochemically. The allylstannane function-... 

Miscellaneous Reactions. AICI3 has been used to catalyze the addition of allylsilanes to aldehydes and acid chlorides (eq 37). Cyclic ethers (pyrans and oxepins) have been prepared with hy-droxyalkenes (eq 38). The course of reactions between aldehydes and allylic Grignard reagents can be completely diverted to a-allylation by AICI3 (eq 39). The normal course of the reaction gives y-allylation products. 

The /3-lactone was formed by the cyclization of a 3-hydroxycarboxylic acid with sulfonyl chloride. An alternative synthesis attempted to control all stereochemical relationships in the molecule using the properties of silyl moieties attached to substrates and reagents <20040BC1051>. Stereoselective reactions of this type included the use of silyl groups in enolate alkylations, hydroboration of allylsilanes, and an anti Se2 reaction of an allenyl silane with an aldehyde and ry -silylcupration of an acetylene. The /3-lactone was again formed by the standard sulfonyl chloride cyclization method. 

Acetals and ketals are exceptionally good electrophiles for allylsilanes, often giving better yields than the corresponding aldehyde or ketone, because the products are less prone to further reaction. Typically the reactions are catalyzed by stoichiometric amounts of titanium tetrachloride in dichloromethane at -78 °C, and the regiospecific reaction is complete in a few minutes (Scheme 37). Other Lewis acids used are boron trifluoride etherate, tin(IV) chloride and, in catalytic amounts, trimethylsilyl tri-flate, - trityl perchlorate and montmorillonite clays. With the unsymmetrical acetal (53), the meth-oxyethoxy group departs selectively (Scheme 38), presumably because it chelates the Lewis acid. ... 

It is readily converted to trimethylsilylmethylmagnesium chloride (see [13170-43-9] above) in —90% yield. It reacts with n-BuLi in pentane to give trimethylsilylmethylLi [Sommer et al. J Am Chem Soc 71 2750 1949, which reacts with anhydrous cerium (III) chloride to form trimethylsilylmethyl cerium dichloride. The latter reacts with acyl hahdes to provide bis-p-silylethyl tertiary alcohols that effidently undergo a trimethylchlorosilane-promoted Peterson reaction to generate allylsilanes in high overall yields [Anderson Fuchs Synth Commun 17 621 7987]. It is useful also for Peterson olefination and homologation of aldehydes and ketones via 1,2-epoxysilanes [Lee et al. Tetrahedron 45 5877 7989]. Trimethylsilylmethyl bromide [18243-41-9] has M 167.1, b 115.5 /atm, 1.17, Up 1.444 [Beilstein 4 IV 3878], and trimethylsilylmethyl iodide [4206-67-1] has M 214.1, h 139-141 /atm, df 1.433, ng 1.491 [Beilstein 4 IV 3878], and both should be stored in the dark. 

The allylation of a carbonyl compound, or equivalent thereof (aldehydes, ketones, acetals, ketals, enones, acid chlorides, epoxides, etc.), performed with an allylsilane 39 promoted by a Lewis acid (TiCl, SnCl, BF3-OEt2, AICI3, EtjAlCl, etc.) is known as Hosomi-Sakurai reaction (Scheme 12.11, Eq. 1) [68, 69]. This reaction was first described in 1976, allowing the synthesis of homoallylic alcohols 43 from aldehydes and ketones 40 [70]. A year later, the authors extended the method to ketals 41, which provide homoallylic ethers 44 (Scheme 12.11, Eq. 2) [71], and to a,p-unsaturated ketones 42 (Scheme 12.11, Eq. 3) [72]. 

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