Tributyltin deuteride

The most commonly used method for synthesizing organotin hydrides with a hydrogen isotope bonded to the tin atom is to reduce the appropriate chlorostannanes with labelled hydride reagents, such as lithium aluminium deuteride or sodium borodeuteride. For example, tributylchlorostannane can be reduced with lithium aluminium deuteride42-45 or deuterated or tritiated sodium borohydride46 to give tributyltin deuteride and tritiated tributyltin hydride, respectively (equations 40 and 41). 

Aryl halides can also be reduced by tin hydrides76,77, although these reactions always require initiators because the stronger C—X bonds in aryl halides are less reactive than the C—X bonds in alkyl halides. In fact, a series of meta- and para-substituted bromobenzenes, where X is either meta- or para-CH3O-, C=N, Cl, F, CF3, CH3, Bu-f or 2,6-dichloro, have been reduced by tributyltin deuteride (equation 60). It is worth noting that the more reactive bromide is reduced selectively in the presence of the less reactive chloride and fluoride groups (equation 61). 

John and coworkers78 also observed cyclization to a five-membered ring heterocycle in their hydride reduction of methyl 6/i-isothiocyanatopenicillanate with both tributyltin hydride and triphenyltin hydride (Scheme 16). John and coworkers also found this type of ring closure when an isocyanide was reduced with tributyltin deuteride. The mechanism of this arrangement (Scheme 17) has been confirmed by deuterium labelling. 

Many other groups can be selectively reduced by organotin hydrides. Although these reactions have not been used to date to form labelled compounds, the reactions are included here using tributyltin deuteride as the reducing agent to illustrate the synthetic possibilities for this reagent. 

Tributyltin deuteride has also been used to help determine the mechanism of the electrochemical oxidation of carbonylmanganese phosphites and carbonylmanganese phosphines (equation 113). 

In one study, Ingold and coworkers166 measured the rate constants for the reactions of several alkyl radicals with tributyltin hydride using a laser flash photolytic technique and direct observation of the tributyltin radical. They also used this technique with tributyltin deuteride to determine the primary hydrogen-deuterium kinetic isotope effects for three of these reactions. The isotope effects were 1.9 for reaction of the ethyl radical, and 2.3 for reaction of the methyl and n -butyl radicals with tributyltin hydride at 300 K. 

Vinylcyclobutanones with a cA-(2-iodoethyl) or c -(2-bromoethyl) substituent in the 2-position rearranged in a complicated sequence. Tributyltin deuteride reduction allowed an assignment of the migrating atoms for example, rearrangement of 3 to 4a or 4b.116-117 148... 

A solution of the product from Step 1 (0.03 mmol) dissolved in 0.3 ml THE was added to a mixture of tributyltin deuteride (0.045 mmol) and triethyl borane (0.004 mmol) dissolved in 0.7 ml THE and the reaction stirred at ambient temperature 3 hours. Thereafter, the solvent was removed, the residue dissolved in 1 ml acetonitrile, extracted 5 times with 1 ml hexane, and the product isolated in 38% yield, mp = 190 °C m/z = 206. 

In reduction of arenediazonium fluoroborate with tributylstannane, formation of the arene takes place not only by hydrogen atom abstraction from the stannane, but also by reaction of the radical interm iate with the solvent. Reduction of 4-methoxybenzenediazonium fluoroborate with tributyltin deuteride in te-trahydrofuran or acetonitrile affords not only deuterated but also deuterium-free arenes (equation 89). There are also small amounts of biphenyl by-products. ... 

Reductions with tributyltin deuteride (BujSnD) showed that the microstructure of the butyl branches is 2,4-dichlorobutyl with a chlorine attached to the branch carbon, i.e. a tertiary chlorine. 

Under heating in THE (65°C) in the presence of tributyltin deuteride and AIBN, a mixture of products (2 R 2 S = 82 18) is obtained in 93% yield. The selectivity of the sonochemical experiments run at - 71 C reaches 96 4, the highest obtained in comparison to other methods, even if the thermal reaction with triethylborane and tributyltin deuteride provides higher yields (90%). 

The conformational change from the chair form in the radical precursors to the boat form in the anomeric glycosyl radicals is so rapid that stereochemical memory is lost upon the generation of the radical. Thus, the reduction of P- and a-haloglycosides 1 and 7 by tributyltin deuteride afforded a-deuterated product 8 regardless of the stereochemistry of the starting materials (Scheme 4). ... 

---