Organotin hydrides decomposition

These compounds were obtained from the LiAlH4 reduction of the corresponding triorganotin bromides (vide infra). It should be noted that it is rather unexpected that these compounds are stable, since it is well known that amines catalyze the decomposition of organotin hydrides to ditin compounds and hydrogen (107). 

A new decarboxylative route to free radicals, which has proved particularly successful in preparative work, embodies the thermal (or photochemical) decomposition reaction of 1-hy-droxypyridine-2(l/f)-thione esters 23 with tributyltin hydride, /er/-butanethiol, or a similar hydrogen donor.These esters can be easily prepared from acyl halides and the sodium salt of l-hydroxypyridine-2(l//)-thione, or from the carboxylic acid, dicyclohexylcarbodiimide and l-hydroxypyridine-2(l/f)-thione. The intermediate radicals were readily reduced to the corresponding hydrocarbons 24 in efficient chain reactions with organotin hydrides or thiols as reaction partners, and the proportion of rearranged to unrearranged products could be controlled by the choice of hydrogen donor, its concentration and the temperature. This system was sufficiently quantitative and well behaved for use in kinetic studies, and the rate constants of the (S-scission reactions of the listed cyclopropylmethyl species were determined. 

The decomposition of organotin hydrides is catalysed by amines. The dihydrides yield cyclic compounds e.g. 

Radical formers as catalysts were of no help they mostly accelerated the decomposition of Bu3PbH. Also catalysis by aluminum alkyls 189,201), used for the addition of organotin hydrides to olefins, is not useful because the transfer of an alkyl group to RjPbH depends upon the necessary addition of R2AIH to the olefin 189, 284) at 20° C (which is the limit for the stability of the organolead compounds used) and this does not take place. 

Two alternative routes, which have been little exploited, are the thermal decomposition of an organotin formate, or the hydrolysis of a stannylmetallic compound, and a promising different approach involves the alkylation of a lithium tin hydride. 

This access to a , y-bis(tricyclohexyltin)alkanes proves to be very convenient when the corresponding organic dihalides are available. When this is not the case, and when a , y-dienes are more easily accessible, a double hydrostannation of these unsaturated compounds can be used. As indicated above, this radical addition has to be conducted in less mild conditions than for the addition of tri-n-butyltin hydride, for instance, because of the bulkiness of the organotin center and also of the more nucleophilic character of the tricyclohexyltin radical. Nevertheless, the treatment of 4,4 -di(butenyl)biphenyl or 4,4 -bis(but-3-enyloxymethyl)biphenyl with tricyclohexyltin hydride at 130 °C over seven days affords the corresponding adducts 72 and 75 in good yields (Scheme 3.7.11). Due to its rapid decomposition at this temperature, the AIBN initiator has to be added in small portions for the duration of the reaction. 

Since triphenyltin hydride tends to interact with benzoyl peroxide to yield triphenyltin benzoate and other products (44) > a peroxide-catalyzed addition of this hydride to olefins is overshadowed by decomposition products. However, polar unsaturated compounds such as acrylonitrile add triphenyltin hydride readily via a supposed ionic mechanism (122,123). The reaction offers a new pathway to functional organotin derivatives of high biocidal activity ... 

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