Tributylstannyl hydride

A novel homolytic substitution yielded 2-(tributylstannyl)benzothiazole [35]. Thus, 2-(alkylsulfonyl)benzothiazole 49 was allowed to react with 2 equivalents of tributyltin hydride in the presence of catalytic azobisisobutyronitrile (AIBN) in refluxing benzene, affording 2-(tributylstannyl)benzothiazole along with tributylstannylsulfinate 50. 

Vinylic radicals, generated by tributyltin hydride addition on triple bonds, also add on 2,3 double bonds [80,81]. One advantage of this method is the presence of a tributylstannyl-... 

Imidazole or pyridine mediated silylation of l,2-0-[l-exo-ethoxy )ethylidene]-oc-D-glucopyranose failed to give a high yield of the 6-silyl ether due to some polymerization and side reactions. Activation of hydroxyl groups via a tributylstannyl intermediate followed by the tetrabutylammonium bromide catalyzed reaction with tert-butyl-chlorodiphenylsilane was more successful [231], the 6-0-silyl derivative being isolated in 87 % yield.. The lability of this protecting group under benzylation with benzyl bromide and sodium hydride at 0 °C has been observed [449]. 

The transformation of 6-bromo-l-hexene (38) into methylcyclopentane by the action of tributyltin hydride (Scheme 7) typifies the richness of the C—C bond forming chemistry in question. A knowledge of the critical rate constants (kc, ku and Br in Scheme 7) allow, through control of substrate concentration, necessary selectivity criteria to be met. Specifically the 5-hexenyl radical (39) must undergo intramolecular addition to form the cyclopentylmethyl radical (40), 40 must abstract a hydrogen atom from tributyltin hydride and the tributylstannyl radical must abstract the halogen in 38 to form 39. These processes must proceed faster than any competing side reaction. 

Distannylethenes are traditionally prepared by the free-radical addition of a tin hydride to a vinyltin the bis(tributylstannyl) derivative has been used in either single or double coupling reactions, for example by Echavairen and co-workers [52,53], who reacted it with acid chlorides, and Barrett et al. [54], who coupled it sequentially with alkenyl iodides. 

An alternate radical-induced addition-fragmentation sequence relies on the 1,4-elimination of a leaving group to drive the reaction. In this sequence, because the fragmentation is accompanied by the expulsion of a tributylstannyl radical, the requirement for the initial tributyltin hydride is only catalytic (Scheme 79). The stereospecificity of the reaction course has been rationalized in terms of a conformational preference for the elimination step, as depicted in Scheme 79 where the rrans-substituted cyclohexanone forms only one double bond geometry in the product. As shown in equations (40) and (41), the cij-substituted cyclohexanones undergo the four- and three-carbon expansions stereospecifically to give the (Z)-alkenes. 

A mixture of tributylstannyl N,N-pentamethylenecarbamate and NaBH4 in ether heated with vigorous stirring for 4 h tributyltin hydride. Y 60%. F.e.s. N.A. Boldyreva et al., Zh. Obshch. Khim. 58, 1181-2 (1988). 

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