Allyltributylstannanes

The reaction between primary and secondary halides and allyltributylstannane provides another method for unsymmetrical coupling RX + CH2=CHCH2 SnBu3 RCH2CH=CH2. ° ... 

Dioxopentane-3-thione reacts178 with allyltributylstannane, Scheme 14, to give the expected thiophilic ene adduct and a [2+2] cycloadduct. 

Addition of allylic zinc bromides to nitrones, generated in situ from allylbro-mides and zinc powder in THF (670), allyltributylstannane (671) and lithiated allyl ferf-butyldimethylsilyl ether (672), proceeds regioselectively in good yields and is used to synthesize homoallyl hydroxylamines (Scheme 2.189). The latter were subjected to an iodo cyclization reaction (see Scheme 2.186). 

A 25 x 17-cm silica gel (Davisel 633) column is used. Initially, hexanes are used as eluant to elute recovered allyltributylstannane, then 9 1 hexane acetone is used as eluant to isolate the product. Further elution of the column with 8 2 hexane acetone gives 0.9 g (80%) of crude recovered BINOL which can be further purified by chromatography over silica gel to give 0.8 g (70%) of pure BINOL. 

Benzyloxyacetaldehyde Acetaldehyde, (phenylmethoxy)- (9) (60656-87-3) Allyltributylstannane Stannane, allyltributyl- (8) Stannane, tributyl-2-propenyl- (9) (24850-33-7)... 

Allyltributylstannane is commercially available (Aldrich Chemical Company Inc.) or can be easily prepared following an Org. Synth, procedure.2... 

Another general synthesis of homoallylamines is the conversion of the trifluoroacetate of a primary or secondary amine into the corresponding inunonium salt by the action of aqueous formaldehyde, followed by successive treatment with allyltributylstannane and dilute hydrochloric acid e.g. equations 69 and 70 (TFA = CF3 CO2)195. 

The ability to conduct radical reactions without the use of tin reagents is important. Allylic triflones have been used to conduct allylation reactions on a range of substrates (39) as a replacement for allyltributylstannane (Scheme 28). The main limitation was that unactivated or trisubstituted triflones failed to undergo reactions. In other nontin radical methods, arenesulfonyl halides have been used as functional initiators in the CuCl/4,4 -dinonyl-2, 2 -bipyridine-catalysed living atom-transfer polymerization of styrenes, methacrylates, and acrylates.The kinetics of initiation and propagation were examined with a range of substituted arylsulfonyl halides with initiator efficiency measured at 100%. 

Intramolecular hydrogen abstraction by primary alkyl radicals from the Si—H moiety has been reported as a key step in several unimolecular chain transfer reactions [11]. In particular, the 1,5-hydrogen transfer of radicals 8-11 (Reaction 3.4), generated from the corresponding iodides, was studied in competition with the addition of primary alkyl radicals to the allyltributylstannane and approximate rate constants for the hydrogen transfer have been obtained. Values at 80 °C are in the range of (0.4-2) x 10" s, which correspond to effective molarities of about 12 M. 

Certain organostannanes have been shown to react with DMAD to give simple addition products. Thus, the reaction of allyltributylstannane with DMAD gives the 1 1 adduct 508 [Eq. (75)] whereas crotyltributylstannane gives the adduct 509, occurring through an allylic type of rearrangement [Eq. (76)]. ... 

We also tried to trap the presumed intermediate radical A using acrylonitrile, butyl vinyl ether or allyltributylstannane as the trapping reagents. In the first two cases mixtures of the 2-deoxy-lactone 65 and the C-2-alkylated product were obtained. Treatment of 20 with allyltributylstannane gave 68 as a homogeneous product (Scheme 14) in a fully stereocontrolled reaction [45,98b]. 

In addition to allylsilanes, CM can also be applied to allylstannanes, which serve as valuable reagents for nucleophilic additions and radical reactions.To date, only eatalyst 1 has been shown to demonstrate CM reactivity in the preparation of 1,2-disubstituted allylstannanes, as ruthenium catalysts were found to be inactive in the presence of this substrate class.Poor stereoselectivities were generally observed, with the exeeption of one instance of >20 1 Z-selectivity in the reaction of allyltributylstannane with an acetyl-protected allyl gluco-side. 

A solution of thionocarbonate 86 (11.16 mg, 26.8 mmol) [Eq. (16)] in 54 mL of toluene was placed in a Hanovia photolysis apparatus and allyltributylstannane (17.68 mg, 53.6 mmol) was added. After thoroughly degasing the solution with argon, it was irradiated during 65 h at room temperature with a 450-W Hanovia lamp with Pyiex filter. Solvent was removed under reduced pressure, and the crude product was purified by chromatography over silica gel (ether-hexane, 5 95) affording 87 (6.25 g, 80%) as a colorless oil mp 43°-44°C [a]D -70.3° (c 0.08, CH2C12). 

A sequence of reactions that was recently reported by Hanessian and Alpegiani nicely illustrates how the allylstannane method is useful for functionalization of complex, sensitive substrates and, more generally, how stereochemistry can be controlled in radical addition reactions (Scheme 40).138 Dibromo- 3-lac-tam (25) can be monoallylated with a slight excess of allyltributylstannane and then reduced with tributyltin hydride to provide 3-allylated (3-lactam (26) (the acid salt of which shows some activity as a 3-lactamase inhibitor). Stereochemistry is fixed in the reduction step hydrogen is delivered to the less-hindered face of the radical. Alternatively, monodebromination, followed by allylation, now delivers the allyl group from the less-hindered face to provide stereoisomer (27). Finally, allylation of (25) with excess allylstannane produces the diallylated product (not shown). 

In 1998, Yamamoto et al. reported the first catalytic enantioselective allylation of imines with allyltributylstannane in the presence of a chiral 7i-allylpalladium complex 23 (Scheme 9) [15]. The imines derived from aromatic aldehydes underwent the allylation with high ee values. Unfortunately, the allylation reaction of aliphatic imines resulted in modest enantioselectivities. They proposed that a bis-Jt-allylpalladium complex is a reactive intermediate for the allylation and reacts with imines as a nucleophile. The bis-Jt-allylpalladium complex seemed the most likely candidate for the Stille coupling [16]. Indeed, the Stille coupling reaction takes place in the presence of triphenylphosphine even if imines are present, whereas the allylation of imines occurs in the absence of the phosphine [17]. They suggested the phosphine ligand played a key role in controlling the... 

An interesting enantioselective addition-allyl-transfer sequence of an electron-deficient alkene 163 with alkyliodides and allyltributylstannane 164 was described... 

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