Butyltin hydride, reaction with

In an attempt to resolve this dilemma, the reaction rates were measured for a series of organic bromides with sodium anthracene (Table I) and correlated with two model systems. The model for the first possibility, a one-step process with bond dissociation, is the tri-n-butyltin hydride reaction with these same halides (6 ). Correlation of the reaction rates would indicate that the transition state for anthracene radical anion reduction is similar to the transition state for radical formation by tri-n-butyltin radical. On the other hand, the model for the second possibility, the organic halide reduction potential, is a measure of organic halide radical anion formation (7). 

Recently, Kondo and coworkers reported on the polymerization of St with diphenyl diselenides (37) as the photoiniferters (Eq. 39) [ 162]. In the photopolymerization of St in the presence of 37a and 37b, the polymer yield and the molecular weight of the polymers increased with reaction time. The chain-end structure of the resulting polymer 38 was characterized. Polymer 38 underwent the reductive elimination of terminal seleno groups by reaction with tri-n-butyltin hydride in the presence of AIBN (Eq. 40). It also afforded the poly(St) with double bonds at both chain ends when it was treated with hydrogen peroxide (Eq. 41). They also reported the polymerization of St with diphenyl ditelluride to afford well-controlled molecular weight and its distribution [163]. 

In the presence of the hydrogen donor tri-Af-butyltin hydride, only hydroxamic ester 195 is formed and the reaction is presumed to involve N—O bond homolysis to give the resonance-stabilized Af-alkoxyamidyl radicals (198), which in the presence of BusSnH are reduced to hydroxamic ester according to Scheme 30. In the absence of BusSnH hydride, formation of esters probably involves alkoxyamidyl dimerization to hydrazines (199) as intermediates (see Section Vl.C, Scheme 34), although HERON reactions of 194 with production of methoxynitrene cannot be discounted. Mesityl radicals, formed by the... 

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... 

A solution of 6.13 g (12.8 mmol) of the l-f/-imidazole-l-carbothioate, 5.15 mL (19.1 mmol) of tri-n-butyltin-hydride and 0.12 g A1BN in 120 mL of dry toluene was refluxed for 1 h. An additional 0.5 eq of Bu3SnH and 60 mg of AlBN were added and the refluxing was continued for 1 h longer. The reaction mixture was added to 400 mL of ether, and it was washed with 80 mL each of saturated KF, 1 N HC1 and saturated NaHCOj. The organic layer was washed with three 50-mL portions of saturated potassim fluoride and dried over anhydrous MgS04. Concentration and chromatography of the crude mixture yielded 3.59 g (58% from the enitol) of the desired product (6b, Y = OMe) [a]D —23.8 0.8° (c 1.0, CHClj). 

Reduction of acyl chlorides to aldehydes,13 Tri-n-butyltin hydride reduces acyl chlorides to a mixture of aldehydes and esters. In the presence of a soluble Pd catalyst usually Pd[P(C6H5)3]4, only aldehydes obtain. This reduction is very general, and yields are usually > 80%. Reduction of double bonds is a minor competing reaction with a, / -unsaturatcd substrates (< 5% reduction). Of other reducible groups, only an allylic bromide group competes with the COC1 group. 

Wharton reaction (1, 439 8, 245). This reaction can also be conducted under free-radical conditions of reduction of thiocarbonylimidazolide derivatives of a,/l-epoxy alcohols with tri-n-butyltin hydride.17 In some cases, inverse addition is necessary to prevent further rearrangement of the allylic alcohol initially formed. Yields are around 50-60%. The modification is not useful in the carbohydrate field, where very complex product mixtures are formed. 

A Iky I-1.7>-hutadienes.311 A radical reaction of tri-n-butyltin hydride with a-(llydmxymclhyl)allyl lolyl sullbncs (I) results in stereoselective formation of allyltin intermediates, which fragment to 2-substilutcd 1. .Vbutadicnes when heated. 

These reactions were applied to the synthesis of phenol derivatives [32], aminoglycoside antibiotics [33] etc.. . and are of great interest in other synthetic applications, b) In the field of substitution reactions, a more recent application of photobromination reactions is described for the synthesis of L-iduronic acid derivatives from D-glu-curonic acid analogs 26. The C-5 photobrominated product 27 is reduced with tri-n-butyltin hydride to give a mixture of starting material and the L-idopyranuronate 28 by a supposed rapidly interconverting radical [29] (Scheme 14). 

Tri-n-butyltin hydride is obtained by reaction of Bu3SnCl with excess LAH in ether (4). 

RX RCHO. Alkyl halides can be converted directly into aldehydes in moderate to high yield by reaction with carbon monoxide (1-3 atm.) and tri-n-butyltin hydride catalyzed by the palladium(O) complex. The reaction involves insertion of carbon monoxide to form an acyl halide, which is known to be reduced to an aldehyde under these conditions (10, 411). Direct reduction of the halide can be minimized by slow addition of the tin hydride to the reaction and by an increase in the carbon monoxide pressure. 

Overall reductive decarboxylation of a carboxylic acid may be achieved by the reaction of the derived acyl chloride with triisopropyisilane (equation 12). Relatively high temperatures are required to bring about efficient decarbonylation of die intermediate acyl radical. A related mediod involves the reaction of acyl phenyl selenides with tri-it-butyltin hydride. Here again relatively high temperatures are required for primary and secondary, although not for tertiary, acids (equation 13). 

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