Ditin reaction with

Reaction with alcoholic silver nitrate has been used as a qualitative test for the ditin linkage, and a variety of compounds, including aryl derivatives, have been shown to deposit a silver mirror on treatment with the reagent (195, 198, 200, 215, 244). Potassium permanganate is also reduced readily (200,265). Hexaphenylditin has been shown to react virtually quantitatively to produce triphenyltin hydroxide when subjected to the action of potassium permanganate in acetone solution (265). 

The propagation steps of these chain reactions are given in Scheme 12, which represents a plausible mechanistic rationalization of the results. That is, Bu Sn radical, initially generated by photolysis of ditin, reacts with alkyl halide to form an alkyl radical that attacks the allyl sulfide (Sh2 process) to give the desired product and thiyl radical. The displacement reaction from ditin gives the Bu Sn radical, thus completing the cycle of this chain reaction. An intramolecular version of this process (equation (43)) has been introduced by Ueno et ai [89a] and later applied by Boger and Wysocki as a key step in multistep synthesis of some natural products [89b]. 

Using alkyllithium compounds, a distannane with a very long Sn—Sn bond, 3.03A, and a syw-peripheral conformation122 was prepared. Thus, reaction of di-t-butyl(chloro)2,4,6-triisopropylphenyl)tin, 78, with f-butyllithium gives 1,1,2,2-tetra-f-butyl-l,2-(2,4,6-triisopropylphenyl)ditin, 79, which displays a restricted rotation about the Sn—C bond as well as the Sn—Sn bond, even at high temperatures. 

Reactions of triorganotin hydrides with amines resulted in the formation of the corresponding ditin species according to equation 4454- 56. 

The preparation of stannylthiazoles via ditin chemistry has not been widely utilized. In one case, the synthesis of 4-tributylstannylthiazole 43 started with selective halogen-metal exchange at C(2) by treating 2,4-dibromothiazole with n-BuLi [33]. Trapping the resulting 2-lithio-4-bromothiazole with propanal and subsequent Jones oxidation secured 4-bromothiazole 42. The Pd-catalyzed reaction of 42 with hexamethyldistannane in the presence of PdCWPhjP provided 4-tributylstannylthiazole 43. 

Unfortunately, application of the ditin chemistry can not be generalized. For instance, simple bromothiazole was recalcitrant towards such a method. Treatment of 44 with hexamethyldistannane in the presence of PdCl2(Ph3P)2 gave dimerized product 45 and debrominated product 46 as the two major products [34], Nevertheless, the both the isolation of the dimer 45 and NMR evidence indicated that the desired 2-stannylthiazole from 44 was generated during the course of the reaction. Thus, trapping the stannane in situ was... 

Synthetically useful allylstannanes are provided by palladium-catalyzed carbostan-nylation using hexamethylditin (Scheme 16.58) [63]. The reaction mechanism can be rationalized by transmetallation between ditin and a Jt-allylpalladium complex produced by reaction of an allene with an arylpalladium iodide. In this process, hexamethylditin is added to the reaction mixture slowly via a syringe pump to suppress its high reactivity towards the arylpalladium species leading to an arylstannane. 

Trimethyl(trifluoromethyl)tin was first prepared via reaction of hexamethyl-ditin with excess iodotrifluoromethane under pressure at 80 °C [101]. Later this reaction was accomplished with ultraviolet light for the preparation of longer chain perfluoroalkyl analogs [102,103] (Scheme 36). 

This result is particularly interesting since no reaction occurred when such ditins were heated with elemental sulfur under similar conditions. The enhanced reactivity of the triorganostibine sulfide in these reactions may be attributed to the semipolar Sb—S bond. 

Ollivier and Renaud built on his new ditin-mediated radical azidation with benzenesulfonyl azide [125] to introduce tandem intramolecular cyclization-azidation processes [126]. For example, iodoacetal 131 provides the corresponding tertiary azide 132 in high yield as a 3 2 mixture of endolexo diastereoisomers (Scheme 41). The necessify of using ditin reagents still constitutes a drawback in this method, as DLP-mediated tin-free reaction conditions failed due to an inefficient chain process. 

Overman and co-workers [75] prepared alkenyltins via a vinyl triflate/ditin coupling. Mitchell and Kwetkat developed a simple route to acyltrimethylstannanes [187], whereas Hitchcock et al. [ 188] carried out a three-component tandem coupling reaction by reacting a 2-pyridyl triflate, aryl or heteroaryl bromides, and hexamethylditin with Pd(PPh3)4 the presence of LiCl to give azabiai yls (Scheme 4-48). 

Wang and Scott [189] have described a two-step reaction in which an iodopyrrole is reacted first with hexabutylditin and subsequently with an aryl or heteroaryl halide unfortunately two different catalysts are required. Bates and Parker [190] have carried out the two-step synthesis of a ligand designed to impose a tetrahedral coordination geometry, the product of the initial ditin/aryl iodide coupling reacting further with a heteroaryl halide without change of catalyst (Scheme 4-49). 

In a first attempt and with the results of the non-symmetrically substituted tetraorganodistannoxanes 1 and 2 in mind, we looked at the reaction of the trimethylene-bridged ditin compound RCl2Sn(CH2)3Sn CI2R (36, R = Me3SiCH2) with cycto-(/-Bu2SnO)3(Scheme 2.10.10). 

The hexanuclear organotinoxo cluster 90 that is based on a spacer-bridged ditin compound is obtained by reaction of thelO-membered ring cycto-CH2[CH2Sn(Cl2)CH2SiMe2]20 with cycto-(t-Bu2SnO)3 (Scheme 2.10.17). 

The reaction of o, y-dibromomagnesioalkanes with tricyclohexyltin chloride leads to the expected ditins 62, 65, 67, and 70, separated by up to 10 methylene groups in high yields (Scheme 3.7.10).22... 

In Grigg s approach to hippadine (44), the biaryl carbon-carbon bond was generated via a Stille-Kelly reaction [42]. Treatment of 42 with hexamethyl ditin in the presence... 

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