Allyltrimethylsilane 1,4-addition

TiCLi-induced conjugate addition of allyltrimethylsilane to 4-phenylbut-3-en-2-one ... 

Initial attempts to effect addition of allyltrimethylsilane with compound 132 under conditions developed in Kishi s C-glycoside work were plagued by epimerization of the acetal center subsequent to the coupling event, providing 133 as a 1 1 mixture of diastereomers (Eq. 21). Boons reported that acetal... 

The alkoxysiladioxanes described by Davis were shown to undergo selective axial addition of allyltrimethylsilane [49]. Moderate selectivity (7-13 1) was observed when the reactions were promoted by Lewis acids (TMSOTf, SnCl4), while higher selectivity was realized when a Bronsted superacid was used (Eq.23). 

Additions of silylated ketene acetals to lactones such as valerolactone in the presence of triphenylmethyl perchlorate in combination with either allyltrimethylsilane 82, trimethylsilyl cyanide 18, or triethylsilane 84b, to afford substituted cyclic ethers in high yields have already been discussed in Section 4.8. Aldehydes or ketones such as cyclohexanone condense in a modified Sakurai-cyclization with the silylated homoallylic alcohol 640 in the presence of TMSOTf 20, via 641, to give unsaturated cyclic spiro ethers 642 and HMDSO 7, whereas the 0,0-diethyllactone acetal 643 gives, with 640, the spiroacetal 644 and ethoxytrimethylsilane 13b [176-181]... 

The weaker Lewis add TMSOTf 20 as catalyst gives, after 2 h at 0°C in CH2CI2, a 20 80 mixture of 805 and 806 in only 23% yield (Scheme 6.8). But this yield will probably increase either on longer reaction time at 0°C or on shorter reaction time at 25 °C On replacing one of the methyl groups in 804 by an acetylene substituent the resulting enyne adds allyltrimethylsilane 82 or anisole in the presence of TMSOTf 20 to give allenes [18]. Substituted allyltrimethylsilanes such as 808 react with the allylic silylether 807 after 70 h at 25 °C in 62% yield to a 41 59 mixture of 809 and 810 as well as 7 [17]. Closely related additions of 82 to allylic ethers or O-acetates are discussed in Refs. 17a-c. 

Reaction of pyridine N-oxide 860 with excess allyltrimethylsilane 82 affords, via 947, 2-propenylpyridine 948 in 53% yield as the only reaction product which can be isolated. Ehmination of trimethylsilanol 4 from 947 is apparently followed by fluoride-catalyzed isomerization of 2-allylpyridine into 2-propenylpyridine 948. 3-Methylpyridine-N-oxide 867 a is converted into 2-propenyl-3-methylpyridine in 69% yield. Likewise, fluoride-catalyzed addition of excess benzyltrimethylsilane 83 to 860 furnishes, via 949, 2-benzylpyridine 950 in 70% yield. The generated leaving group trimethylsilanol 4 reacts with excess allyltrimethylsilane 82 or benzyltrimethylsilane 83 in the presence of fluoride to give hexamethyldisiloxane (HMDSO) 7 and propylene or toluene, respectively [60] (Scheme 7.16). 

Although these reactions are formulated as ionic reactions via 947 and 949, because of the apparent partial formation of polymers and inhibition of the fluoride-catalyzed reaction of pyridine N-oxide 860 with aUyl 82 or benzyltrimethylsilane 83 by sulfur or galvinoxyl yet not by Tempo, a radical mechanism caimot be excluded [61, 62]. The closely related additions of allyltrimethylsilane 82 (cf. Section 7.3) to nitrones 976 are catalyzed by TMSOTf 20 to give, via 977, either o-unsatu-rated hydroxylamines 978 or isoxazoHdines 979 (cf also the additions of 965 to 962a and 969 in schemes 7.20 and 7.21). 

Compound 976 c, however, gives, after addition of allyltrimethylsilane 82, via exclusive 1,3-dipolar cydoaddition of allyltrimethylsilane 82, only 5-trimethylsilyl-methylisoxazohdine 979c [71, 72] (Scheme 7.22). 

Addition of allyltrimethylsilane 82 to 3,4,5,6-tetrahydropyridine-N-oxide (readily accessible, primarily as the dimer, on HgO-oxidation of N-hydroxypiperidine) in the presence of BU4NF 2-3H2O in TH Faffords 2-propenyl-N-hydroxypiperidine [72 a]. 

Entry 2 was reported as part of a study of the stereochemistry of addition of allyltrimethylsilane to protected carbohydrates. Use of BF3 as the Lewis acid, as shown, gave the product from an open TS, whereas TiCl4 led to the formation of the alternate stereoisomer through chelation control. Similar results were reported for a protected galactose. 

HfCl4-catalyzed hydro- and carbometalation have been investigated.1 3 /nr/i.v-Addition of tri-butyltin hydride or allyltrimethylsilane to alkynes occurs with high selectivities (Scheme 43).162 In a-olefin polymerization, the Hf mcthylaluminoxanc (MAO) system also works well.184... 

Thus, an Af-acyliminium ion pool 4 was allowed to react with an enamine derivative 8 (Scheme 8). The addition of the cation to the carbon-carbon double bond generated the second cation 9, which seemed to exist either as the open form or the cyclic form. In the next step, cation 9 was treated with allyltrimethylsilane to give the final three component coupling product 10. 

The anodic oxidation of compound 35 resulted in the formation of dication 36 (Scheme 19). 13C NMR indicated that two cationic centers are equivalent. The addition of allyltrimethylsilane to the solution gave rise to the formation of diallylated compound 37 in 80% yield. 

For the addition of ethylene, EtOAc as solvent was particularly advantageous and gave 418 in 60% yield (Scheme 6.86). The monosubstituted ethylenes 1-hexene, vinylcyclohexane, allyltrimethylsilane, allyl alcohol, ethyl vinyl ether, vinyl acetate and N-vinyl-2-pyrrolidone furnished [2 + 2]-cycloadducts of the type 419 in yields of 54—100%. Mixtures of [2 + 2]-cycloadducts of the types 419 and 420 were formed with vinylcyclopropane, styrene and derivatives substituted at the phenyl group, acrylonitrile, methyl acrylate and phenyl vinyl thioether (yields of 56-76%), in which the diastereomers 419 predominated up to a ratio of 2.5 1 except in the case of the styrenes, where this ratio was 1 1. The Hammett p value for the addition of the styrenes to 417 turned out to be -0.54, suggesting that there is little charge separation in the transition state [155]. In the case of 6, the p value was determined as +0.79 (see Section 6.3.1) and indicates a slight polarization in the opposite direction. This astounding variety of substrates for 417 is contrasted by only a few monosubstituted ethylenes whose addition products with 417 could not be observed or were formed in only small amounts phenyl vinyl ether, vinyl bromide, (perfluorobutyl)-ethylene, phenyl vinyl sulfoxide and sulfone, methyl vinyl ketone and the vinylpyri-dines. 

Allyltrimethylsilane (la) reacts with cycloalkenes such as cyclohexene and cyclo-pentene at room temperature to give stereospecifically tra j -l-trimethylsilyl-2-al-lylcycloalkanes. These products are formed through trans addition and an allylic inversion. 

The key step in the approach of Jurczak et al. [59] was a chelation-con-trolled addition of allyltrimethylsilane to the AT-Cbz-protected phenylalani-nal 88 in the presence of SnCl4 (Scheme 24). The preussin C-3/C-4 bond was... 

A [3+3]-type annulation between a,a -dimethoxylated lactam 43 and allyltrimethylsilane gives bicyclic lactam 44. The reaction proceeds presumably through the allylation at the a-position followed by the intramolecular addition of the cation developed at the a -position to the allylic double bond (85JOC3243). The aza-Diels-Alder reaction of... 

The addition of BF3 OEt2 to a solution containing Ph3BiF2, allyltrimethylsilane and excess arenes induces a Friedel-Crafts-type allylation at low temperatures to yield allylarenes [36]. Benzene, toluene, anisole, p-xylene, and p-dimethoxyben-zene were all allylated with ease to give the corresponding allylation products, although diallylation could not be suppressed in the reaction with electron-rich... 

The first procedure is a one-pot sequential process in which the acetal is formed from the aldehyde in a Bi(OTf)3-catalyzed reaction with trialkylorthoformate and the corresponding alcohol. After the aldehyde was consumed, the remaining alcohol was removed under reduced pressure. Acetonitrile, allyltrimethylsilane, and additional Bi(OTf)3 were added and the desired homoallyl ethers were obtained in moderate to good yields (Scheme 10). 

In this chapter, we wish to disclose our results on the nucleophilic addition of carbon nucleophiles to N-alkoxycarbonylamino sulfones. Both allyltrimethylsilane and silyl enolates will be considered as nucleophiles. The corresponding amines were obtained efficiently in the presence of 0.5-5 mol% of Bi(0Tf)34H20 [57,58]. 

Jurczak and Kiegiel reported that additions of allylmagnesium chloride and allyl bromide in the presence of Zn to iV-methyl and W-phenylglyoxyloyl-(2R)-borane-10,2-sultam occurred in a diastereoselective manner. Similarly, the Lewis acid mediated addition of allyltrimethylsilane also gave good diastereoselectivity and in the case with TiCU a change of direction of asymmetric induction was observed <99TL1009>. 

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