Acid chlorides allylic silanes

Furthermore, the use of a Lewis acid promoter leads to increased stereoselectivities (Table 19, entry C)252,254. Compared to the aprotic reaction, where allyl silane was used instead of allyl bromide and indium chloride, an almost complete reversal of the diastereos-electivity was found. It was demonstrated recently that the Lewis acid catalysed allylation reaction can be carried out efficiently without any organic solvent in saturated ammonium chloride solution255. Finally, Lewis acid catalysed Mannich reactions can be carried out conveniently in mixtures of organic solvents and water. However, the exact role of the Lewis acid catalyst has not been clarified (Table 19, entry D)253. The same reaction can be carried out in pure water with catalysis by indium trichloride256. 

Allyl silanes react with a wide variety of electrophiles, rather like the ones that react with silyl enol ethers, provided they are activated, usually by a Lewis acid. Titanium tetrachloride is widely used but other successful Lewis acids include boron trifluoride, aluminium chloride, and trim ethyls ilyl tri-flate. Electrophiles include the humble proton generated from acetic add. The regiocontrol is complete. No reaction is observed at the other end of the allylic system. All our examples are on the allyl silane we prepared earlier in the chapter. 

In the presence of titanium(IV) chloride or aluminum chloride, carbonyl compounds such as aldehydes, ketones, acetals, and acid halides are allylated with allylic silanes (eq (12)) [9]. The conjugate addition to enones is also reported (eq (13)) [10],... 

If neither the halides nor their metal derivatives have a stable structure, how can we expect to control their reactions Things are not quite as bad as that. The bromides and chlorides are stable at low temperatures in the absence of Lewis acid catalysts or radical generators. The Grignard reagents often react cleanly to give the less substituted double bond isomer, presumably by the type of process shown in 12. We shall be seeing methods to control transition metal allyls and allyl silanes which make these intermediates valuable reagents in synthesis, and you should finish this chapter in a confident mood without fear of fluxional allyl compounds. 

An acid chloride functionalized liquid crystalline material was tried to bond to the silanol group in silica. The direct reaction does not seem to be successful also, a spacer with a substituted dichlorodimethyl silane is not successful. The reaction scheme is shown in Figure 16.8. However, a separation performance is observed rather by deposition than by bonding of the liquid crystals. The liquid crystalline materials used in this study was based on cholesteric moieties. It is suspected that the reaction failed because of the large size of the cholesteryl group. In another study, dimeth-ylchlorosilane was added to the allyl group of 4-methoxyphenyl-4-allyloxy benzoate. This intermediate could be bonded to silica. Several other routes to fix liquid crystalline moieties on silica have been reviewed. ... 

C—C Bond Formation using Organosilanes. Under catalysis by TiCU, allylsilanes transfer the allyl group, with rearrangement, to ketones, a/3-unsaturated ketones (conjugate addition), and quinones (initially giving the carbonyl addition product which then further rearranges to the 2-allyl-l,4-hydroquinone). But-3-enyl-silanes react with acid chlorides to yield cyclopropylmethyl ketones [reaction (3)) under similar conditions. 

Homoallyl bromide 314, prepared from readily available non-racemic ester 313, was converted to the Grignard reagent, which reacted with non-racemic epoxide, derived from D-maUc acid, to afford the alcohol 305. Ozonolysis of the alkene gave a ketone, which was converted into enol tri-flate 316. Ni-catalyzed cross coupling with trimethylsilylmethyl magnesium chloride afforded the allyl silane, which was converted into the allyl stan-nane 317. The asymmetric allylation of 313 with 317 provided 304 with a ration of 8.5 1. Methyl etherification and oxidative cleavage of exo-methylene... 

Isoprenylation. Like other allylic silanes, 2-trimethylsilylmethyl-1,3-butadiene reacts with various electrophilic species such as acetals, acid chlorides, and carbonyl compounds with the aid of a Lewis acid to give the corresponding isoprenylated compounds (eqs 3-6). 

We have previously reported on the synthesis of a series of mono- and bifunctional poly(DMS) having a variety of reactive end groups, such as silan (Si-H), vinyl, hydroxyalkyl, dimethylamino and carboxyllic acid groups.7 We have also described already on telechelic poly(DMS) having tosylate end group, lb and l b, where the hydrosilation reaction of poly(DMS) having silan end group was performed with allyl alcohol in the presence of Pt/C catalyst, followed by the tosylation reaction with tosyl chloride in the presence of dimethylaminopyridine.9... 

If the electrophile also benefits from Lewis acid catalysis, as in the aliphatic Friedel-Crafts reaction, good yields of products are generally found. The anion of the allyl phosphonate 192 can be silylated to give the vinyl silane 193 and this reacts in turn with the classical combination of acetyl chloride and A1C13 to give the enone -194 that can be used in HWE reactions to make dienones46 (chapter 15). 

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