Allyltributyltin

Quinoxaline with allyltributyltin and 2,2,2-trichloroethyl chloroformate (CICO2-CH2CCI3) gave bis(2,2,2-trichloroethyl) 2,3-diallyl-l,2,3,4-tetrahydro-l,4-quinoxalinedicarboxylate (17) (CH2CI2, 0°C, 3 h 30%) and a separable byproduct, bis(2,2,2-trichloroethyl) 2-aUyl-3-hydroxy-l,2,3,4-tetrahydro-l,4-quinoxalinedicarboxylate (18) (18%). ... 

An extension of the asymmetric condensation of organometallics onto aldehydes is the enantioselective silver-promoted allylation reaction of aldehydes with allyltributyltin, which has recently been performed by Shi et al. in the presence of chiral diphenylthiophosphoramide ligands and more efficiently, with binaphthylthiophosphoramide ligands. According to the nature of the ligand substituents, the corresponding allylation products were obtained in enantioselectivities of up to 98% ee, as depicted in Scheme 3.70. 

Cd. Cadmium perchlorate was found to catalyze allylation reactions using allyltributyltin in aqueous media very efficiently.177 These cadmium-catalyzed allylation reactions are accelerated by ligands such as N, N, N, N", A -pentamethyldicthylcnetri amine or 2,9-dimethylphenanthroline (Eq. 8.75). This accelerated the catalytic system to give allylation products of various aldehydes and ketones in high yields. 

Some 2,3-diazabicyclo[2.2.1]heptene derivatives, for example, 175, with an aryl iodide and allyltributyltin in the presence of [Pd(allyl)Cl]2 in toluene provide unexpected products 176. It is interesting to note that aryl iodide is recovered almost completely but no reaction can be observed in its absence. When the aryl iodide is replaced by a Lewis acid, good yields of 176 are obtained. The reaction is very slow in toluene, but in ionic liquid [bmim]PF6 the reaction rate is significantly enhanced (Equation 21) <2005SL2273>. 

After completion of the reaction, ultrasonic irradiation for an unnecessarily long period causes decomposition of the allyltributyltin. The end of the reaction can be determined by a faint turbidity in the solution and by darkening of the brilliant Mg surface. 

Allyltantalum reagent 124 can be generated by transmetallation of allyltributyltin with tantalum(v) pentachlor-ide.187 Shibata et al. focused on reactions of 124 with a,/3-unsaturated ketones and found, in all cases, that 1,4-addition proceeded in good to excellent yields.187 On the other hand, 124 was later shown to react more smoothly... 

Palladium complexes effectively catalyze the three-component coupling reactions of CC>2461 or isocyanates,462 462 allyltributyltin, and allyl chloride to afford allyl 3-butenoate or iV-tosyl-iV-allyl-3-butenamides, respectively (Equations (104) and (105)). 

Platinum-catalyzed allylation of aldehydes with allyltin reagents was first reported in 1995.4S7 457b,483 483a Ar0matiC) aliphatic, a,/3-unsaturated aldehydes and even cyclohexanone undergo allylation with allyltributyltins in the presence of PtClgtPP 113)2 >n THF at room temperature or higher temperature (Equations (123) and (124)). Allylplatinum species are considered to be the active intermediates on the basis of related mechanistic studies on palladium catalysis. 

As discussed in Section 3.3.2, Corey demonstrated the utility of compound 55, prepared from 1,2-diphenyl-1,2-diamino ethane 54, as a chiral auxiliary for asymmetric aldol reaction. In a similar manner, his group utilized this compound 55 in both (R,R)- and (A,A)-forms for allylation reactions. Treatment of 55 with allyltributyltin in dry CH2CI2 at 0°C and then 23°C for 2 hours gives chiral allyl-borane 135. In this process, both the (R,R)- and (A,A)-forms can be obtained and applied in asymmetric allylation reactions. Thus, treatment of... 

Isoquinoline alkaloids. The regioselective allylation of N-acyl heterocycles (13, 10) can be used for synthesis of isoquinoline alkaloids. Thus simultaneous reaction of the dihydroisoquinoline (1) with a diunsaturated acyl chloride (2) and allyltributyltin affords the 1,2-adduct (3), which undergoes a Diels-Alder cyclization... 

Photolytic allylation of a-phenylseleno ketones.5 a-Phenylselenocycloalka-nones on irradiation with allyltributyltin undergo coupling to give a-allylcyclo-alkanones in generally good yield (equation I). 

Homoallyl ethers or sulfides.1 gem-Methoxy(phenylthio)alkanes (2), prepared by reaction of 1 with alkyl halides, react with allyltributyltin compounds in the presence of a Lewis acid to form either homoallyl methyl ethers or homoallyl phenyl sulfides. Use of BF3 etherate results in selective cleavage of the phenylthio group to provide homoallyl ethers, whereas TiCl effects cleavage of the methoxy group with formation of homoallyl sulfides. 

Allylsilanes in the presence of fluoride ion can be used in place of the Grignard reagents, the reaction of allyltrimethylsilane and bis(tributyltin) oxide giving allyltributyltin in 96% yield.68... 

The Michael allylation of iV-enoyloxazolidinones with allyltributyltin proceeds in good yield with Sn(OTf)4, ZrCU, or Sm(OTf)3 as Lewis acid catalyst.280... 

C-Allyl glycosides can be prepared by the reaction of glycal epoxides with allyltributyltin in the presence of tributyltin triflate as a Lewis acid,281 and aldonitrones can be allylated with trimethylsilyl triflate as a catalyst (Equations (101) and (102)).282... 

The use of allylstannanes for homolytic allylation depends on the rapid conjugate displacement of R3Sn- by attack of a radical at the y-position of the allyl group. The rate constants for this reaction by primary alkyl radicals with the allylstannanes 22 and 23 in Scheme 9 are close to the value that was estimated previously for allyltributyltin.285,286... 

New routes to the alkoxides have been established, starting from the hydrido-, allyl-, or alkynylstannanes. Allyltributyltin and tributyltin hydride react with alcohols in the presence of triflic acid to give the tributyltin alkoxides in good yields,379 and the alkyltrialkynylstannanes are cleaved by alcohols under neutral conditions to give the trialkoxides (Equations (136)—(138)).247... 

A chiral dinuclear Ti(IV) oxide 20 has been successfully designed by Maruoka and coworkers and can be used for the strong activation of aldehydes, thereby allowing a new catalytic enantioselective allylation of aldehydes with allyltributyltin (Scheme 12.18). ° The chiral catalyst 20 can be readily prepared either by treatment of bis(triisopropoxy)titanium oxide [(/-Pr0)3Ti-0-Ti(0/-Pr)3] with (S)-BINOL or by the reaction of ((5)-binaphthoxy)isopropoxytitanium chloride with silver(I) oxide. The reaction of 3-phenylpropanal with allyltributyltin (1.1 equiv) under the influence of 20 (10 mol%) gives l-phenyl-5-hexen-3-ol... 

Transmetallation of allyltributyltin with organolithium species has been used for the generation of allyllithium solutions free of the coupling byproducts which often result from reduction of allylic halides with lithium metal. These solutions may then be used directly for the preparation of Gilman reagents and other reactive modifications of the parent allyllithium. 

The use of allyltributyltin in combination with a Lewis acid has been used to effect both nucleophilic substitution and stereoselective carbonyl... 

By far the most generally useful synthetic application of allyltributyltin is in the complementary set of transition metal- and radical-mediated substitution reactions. When the halide substrates are benzylic, allylic, aromatic or acyl, transition metal catalysis is usually the method of choice for allyl transfer from tin to carbon. When the halide (or halide equivalent) substrate is aliphatic or alicyclic, radical chain conditions are appropriate, as g-hydrogen elimination is generally not a problem in these cases. 

To elucidate the reaction pathway, deuterium-labeled allenyl pinacol boronate 10 was prepared, and the addition reaction with hydrazonoester 6 was conducted in the presence of Bi(OH)3 and Cu(OH)2 (Scheme 4). In both Bi- and Cu-catalyzed cases, the reactions proceeded smoothly (in quantitative yields in both cases). In the Bi(OH)3-catalyzed reaction, a major product was allenyl compound 11, in which the internal position was deuterized. It was assumed that a propargyl bismuth was formed via transmetalation from boron to bismuth, followed by addition to hydrazonoester via y-addition to afford allenyl compound 11. Thus, two y-additions could selectively provide a-addition products [75, 76, 105, 106]. It was confirmed that isomerization of 10 did not occur. Recently, we reported Ag20-catalyzed anti-selective a-addition of a-substituted allyltributyltin with aldehydes in aqueous media [107], On the other hand, in the Cu(OH)2-catalyzed reaction, a major product was propargyl compound 12, in which the terminal position was deuterized. A possible mechanism is that Cu(OH)2 worked as a Lewis acid catalyst to activate hydrazonoester 6 and that allenyl boronate 10 [83-85] reacted with activated 6 via y-addition to afford 12. 

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