Tri-n-butylstannane

C Vinyl stannane coupling 9 3-Bromo-l-(methanesulfonyl)indole Pd(OAc)2, chloranil Z-(2-Etho,xy vinyl)tri-n-butylstannane, Pd(PPh3)2Cl2 83 [9]... 

Reduction by hydrogen atom donors involves free radical intermediates and usually proceeds by chain mechanisms. Tri-n-butylstannane is the most prominent example of this type of reducing agent. Other synthetically useful hydrogen atom donors include hypophosphorous acid, dialkyl phosphites, and tris-(trimethylsilyl)silane. The processes that have found most synthetic application are reductive replacement of halogen and various types of thiono esters. 

More remote oxygen substituents can also influence stereochemistry. 4-Benzyloxy-2-pentenyl tri-n-butylstannane exhibits excellent enantioselectivity in reactions with aldehydes.186 This reaction is believed to involve chelation of the... 

Entry 23 was part of a synthesis of the pancratistatin structure. The lactone ring was used to control the stereochemistry at the cyclization center. Noncyclic analogs gave a mixture of stereoisomers at this center. In this reaction, triphenylstannane gave much better yields than tri-n-butylstannane. 

The results of this study are presented in Table 4.7. As can be seen from the data in Table 4.7, decarbonylation with hydrogen or deuterium transfer to the resulting radical is a relatively efficient process. The failure to observe this reaction using acetone or acetophenone as photosensitizer would suggest a singlet pathway for the direct photolysis of the aldehyde. In agreement, decarbonylation could not be quenched by naphthalene, piperylene, or 1,3-cyclohexadiene when the aldehyde was excited directly. The reaction could, however, be somewhat quenched by the addition of tri-n-butylstannane. The products in this case were... 

It is mentioned in an early paper on the effect of water on Heck vinylations [62] that 2,4-dimethoxy-5-iodopyrimidine reacted with 1-(ethoxyethenyl)-tri-n-butylstannane to afford an acylated pyrimidine derivative in 83 % yield (via in situ hydrolysis of the intermediate enol ether) (Scheme 6.28). 

These reactions result in iodine-atom transfer and introduce a potential functional group into the product. This method of radical generation can also be used in conjunction with either tri-n-butylstannane or tris(trimethylsilyl)silane, in which case the reaction is terminated by hydrogen-atom transfer. 

A solution of per-N-ethoxycarbonylseldomycin factor 5-3 -thiocarbonylimidazolide 51 (Eq. (21)] (12.5 g, 12.58 mmol) in anhydrous dioxane (750 mL) was added dropwise to a refluxing suspension of tri-n-butylstannane (TBTH, 14.0 g, 12.7 mL, 48 mmol) in anhydrous dioxane (1200 mL) under a nitrogen atmosphere. After 2.5 h, the solvent was removed under reduced pressure, and the residue was chromatographed over silica gel to yield 9.8 g (90%) of 3 -deoxy-per-A -ethoxycarbonylseldomycin factor 5 52. 

Irradiations of the unsaturated epoxy ketone (92) in the presence of tri-n-butylstannane at 2537 A (in dioxane) or >3100 A (in dioxane or benzene) produce qualitatively similar mixtures containing products (71), (101),... 

In the palladium-catalyzed addition of allylstannanes to allyl acetates, complete allyl inversion of the allylstannane is observed.137 Symmetrical coupling is also possible, for example, by treatment of cinna-myl acetate with hexa-n-butyldistannane.137 In this reaction, cinnamyl tri-n-butylstannane is generated in situ by Pd catalysis and it then couples with the allyl acetate with allyl inversion (equation 32). 

With this end in view, phenyldimcthylsilyl tri-n-butylstannane was added under the influence of zero-valent palladium compound with high regioselectivity and in excellent yield to the acetylene 386 to give the metallated olefin 387 (Scheme 56). The vinyl lithium carbanion 388 generated therefrom, was then converted by reaction with cerium(lll) chloride into an equilibrium mixture (1 1) of the cerium salts 389 and 390 respectively. However, the 1,2-addition of 389 to the caibonyl of 391, which in principle would have eventually led to ( )-pretazettine, did not occur due to steric reasons — instead, only deprotonation of 391 was observed. On the other hand, 390 did function as a suitable nucleophile to provide the olefinic product 392. Exposure of 392 to copper(II) triflate induced its transformation via the nine membered enol (Scheme 55) to the requisite C-silyl hydroindole 393. On treatment with tetrafluoroboric acid diethyl ether complex in dichloromethane, compound 393 suffered... 

J. R. Rasmussen, C. J. Slinger, R. J. Kordish, and D. D. Newman-Evans, Synthesis of deoxy sugars. Deoxygenation by treatment with AV -thiocarbonyldiimidazole/tri-n-butylstannane, J. Org. Chem., 46 (1981) 4843-4846. 

Lactone 7 (derived from D-isoascorbic acid) reacted readily with the aryllithium formed from bromide 8 to produce lactol 9 (Scheme 16.3). The latter underwent a facile ring-opening and Wittig olefination with methylenetriphenylphosphorane to give 6 in excellent overall yield. After 0-trifLation, a two-carbon chain extension was performed on 10 with the azaenolate derived from A-cyclohexylacetaldimine 11 and lithium diisopropylamine (LDA). After acid hydrolysis of the product imine, aldehyde 12 was isolated in 83% yield for the two steps. The (2-azaallyl)stannane 5 was prepared from aldehyde 12 in quantitative yield by treatment with (aminomethyl)tri-n-butylstannane. 

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