Tri-«-butyltin hydride

Azatriquinacene 39 has been successfully synthesized in three steps starting from azatriquinane 37. Azatriquinane 37 on treatment with sulfuryl chloride under photochemical irradiation gave nonachloride 89 which on reduction with tri- -butyltin hydride provided the 2,3,5,6,8,9-hexachloroazatriquinane 198 in 53% yield. This on treatment with lithium in tert-butyl alcohol gave completely dehalogenated azatriquinacene 38 in an acceptable 32% yield (Scheme 84) <2000JOC7253>. 

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... 

Tri-/ -butyltin hydride also serves as a hydrogen-atom donor in radical-mediated methods for reductive deoxygenation of alcohols.131 The alcohol is converted to a thiocarbonyl derivative. These thioesters undergo a radical reaction with tri-w-butyltin... 

Hydroxypicolinic acid is converted into hexahydrofuro[3,2- ]pyridine-3-one derivative 111 in a nine-step stereoselective synthesis <2004BMC5689>. 3-Iodo-4-prop-2-ynyloxypicolinanilides can be converted into furo[3,2-f]pyr-idine derivatives in good yields in the presence of tri- - butyltin hydride and AIBN <2004H(64)261>. 

Another limitation is seen when extra strain is included in the compound to be reduced. Dehalogenation of 3,3-dichlorobicyclo[2.2.0]hexan-2-one with zinc/ammonium chloride in methanol gave, at best, a 25% yield of 3-chlorobicyclo[2.2.0]hexan-2-one (14) together with cyclohexenone and 6-chlorohex-5-enoic acid.128 The best results were achieved with the zinc/ acetic acid system, while addition of water, silver-promoted zinc reduction in methanol, tri-butyltin hydride reduction or hydrogenolysis with palladium in methanol did not result in formation of 14, but various other ring-opened products. 

Alternatively, novel allenylidene-tetrahydrofurans such as 84 can be prepared by the tri-butyltin hydride-mediated radical cyclization of bromoalkynyl-oxiranes 82, where the epoxide... 

GIESE REACTION Mercury(II) acetate. Tri- -butyltin hydride. 

Trialkyl borates, 398 Tri t-butyltodomethyltin, 475-476 Tri-f-butylsilyl perchlorate, 78 Tri- -butyltin hydride, 476-477 Tributyltin hydride-Silica gel, 477 Tri- U-carbonylhexacarbonyldiiron, 477-478, 519... 

Halohydrin formation with subsequent reductive dehalogcnation represents an interesting variation on the theme. For example, when the enone rac-1 was treated with A -bromosuccin-imide in aqueous dimethyl sulfoxide, the bromohydrin roc-2 was formed, predominantly as one diastereomer (the relative configuration at C-3 was not established)23. Reduction with tri-butyltin hydride gave the diastereomeric products exo-3 and endo-3 in 27% and 63% yield, respectively. Here, the product distribution can be explained by the preferred attack of the hydride reagent on the exo-face of the intermediate bicyclic carbon radical, i.e., by kinetic control. Thus, the predominant endo-orientation of the 2-(2-hydroxypropyl) substituent at C-3 was achieved, in contrast to what may be expected from a reversible, i.e., thermodynamically controlled, hydration of the enone rac-1. 

Hydrogenolysis of the toluene-4-sulfonate of an alcohol may be carried out with a nucleophilic hydride such as lithium aluminium hydride. There are also a series of radical methods based on the reduction of alkyl halides with tri- -butyltin hydride (BUjSnH). Finally, the source of the hydrogen may be the electrophilic proton, exemplified by the decomposition of organometallic reagents such as the Grignard reagent with water. 

Thermal decomposition of AIBN and then hydrogen abstraction from tri- -butyltin hydride. 

The cyclized radical abstracts a hydrogen atom from tri- -butyltin hydride to give the product and a new tri- -butyltin radical to continue the chain. 

TABLE 11. Stereochemistry of reduction of gem-halofluorocyclopropane with tri- -butyltin hydride" ... 

A 5-mM solution of the Z-iodide in dry toluene was degased with argon and heated to reflux. Tri- -butyltin hydride (1.3-1.5 eq) and (10 mol%) ABN in toluene were added by syringe pump over 2-4 h. The solvent was evaporated under reduced pressure and the product was isolated by flash chromatography. Cyclization of 85 mg (0.706 mmol) of substrate gave 58 mg (97%) of the bicyclic product, which was carried on to the next step. A... 

The di-O-tosylates (prepared by action of tosyl chloride in pyridine) are reduced with zinc (Nal/Zn route e Tipson-Cohen reaction) [13]. Cyclic ortho-esters (prepared by reaction of the diol with ethyl orthoformate) are transformed into olefins by simple heating in the presence of acids (Eastwood reaction, route b) [14]. Cyclic thiocarbonates (obtained by reaction of a diol with thiophosgene or (V,(V -thiocarbonyl-di-imidazole) are reduced to olefin with trimethyl phosphite (Corey-Winter method, route c) [15]. Finally, reduction of vicinal di-xanthates with tri- -butyltin hydride according to the Barton procedure [16] affords olefins via a reductive elimination process route a). The Corey-Winter, Garegg, and Tipson-Cohen methods are most commonly applied for deoxygenation of sugar diols. 

A fourth urethane protecting group, the TV-allyloxycarbonyl group (Alloc) is introduced in the usual way using allyl chloroformate or diallyl dicarbonate. Its main interest concerns its removal by a Pd-catalysed hydrostannolysis with tri-butyltin hydride (Scheme 7.4). It thus provides orthogonal protection without the need to expose the peptide to acid, conditions that would cleave, for example, O-gly-coside derivatives of peptides. 

According to the procedure for the endo cyclization of the racemic epoxyalkyne derivatives, optically active cA-epoxide 60 was converted to the corresponding dicobalthexacarbonyl species, which was then treated with a catalytic amount of BF3-OEt2 in CH2CI2 at -78°C to afford the /ron.v-tetrahydropyran derivative 61 in 87% yield (Scheme 14). Demetalation of 61 with CAN was followed by protection of the secondary hydroxyl functionality with a silyl group to afford 62 in 87% yield. Upon consecutive treatment with tri- -butyltin hydride in the... 

DEHALOGENATION l,8-Bis(dimethylamino)napthalene. Lithium diphenylphosphide. Potassium hydridotetracarbonylferrate. Sodium-t-Butanol-Tetrahydrofurane. Sodium borohydride. Sodium iodide. Tri- -butyltin hydride. 

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