Ditin

The Wurtz reaction, which reties on in situ formation of an active organosodium species, is also usefiil for preparing tetraorganotin compounds and is practiced commercially. Yields are usually only fair and a variety of by-products, including ditins, also form ... 

Compounds with Tin—Tin Bonds. The most important class of catenated tin compounds is the hexaorganoditins. The ditin compounds are usually prepared by reductive coupling of a triorganotin haUde with sodium in Hquid ammonia ... 

Lithium metal in tetrahydrofuran can also be used as the coupling reagent, and unsymmetrical ditins can be prepared when the reaction is conducted in stages (162,163). 

The ditins as of yet are insignificant commercially, although there has been interest in hexamethyl ditin [661-69-8] (Pennwalt TD-5032) as an insecticide (164,165). 

If the groups R in RsSnSnRa are very bulky, the Sn-Sn bond is weakened by steric strain, and dissociation can now occur on heating. Hex-akis(2,4,6-trimethyIpheny 1)- and hexakis(2,4,6-triethylphenyl)-ditin can be prepared by heating the corresponding triaryltin hydrides with azoisobutyronitrile (AIBN) (267). 

An improved route to iodomethylzinc iodide has made the iodometh-yltin compounds, R3SnCH2l, more accessible (280). Bimetallic compounds of the types MejSnCBrjMgCl (281), MejSnCClBrLi (282), and MesSnCHIZnI (280, 283), have been prepared in solution at low temperature, and thence, the ditin compounds (MeaSnljCClBr, (MegSnljCBri, (MejSnlaCHI (284). 

The stannylation and silylation of heteroaryl halides has also been studied. The stannylation of 4-iodo pyrimidine was conducted with hexamethyl and hexa-ra-butyl ditin in the presence of fluoride ion and Pd(PPh3)2(OAc)2 as catalyst. The stannylation of 5-bromopyrimidine occurred in the highest yields in the presence of the ligandless catalyst bis(7r-allylpalladium chloride).175 The silylation of bromopyridines, bromopyrimidines, and bromoquinolines also occurred after 96 h at 160 °C with Pd(PPh3)4 as catalyst in HMPT solvent.162... 

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. 

In Grigg s approach to hippadine (37), he established the connection between the two phenyl rings via the Stille-Kelly reaction [45]. When diiodide 35 was submitted to the Pd(0)/ditin catalyst system, the intramolecular cyclization was realized to establish the C—C bond in lactam 36. Oxidation of the indoline moiety in 36 using 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) then delivered hippadine (37). Analogously, the intramolecular Stille coupling of dibromide 38 led directly to hippadine (37) [46]. 

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... 

Dithionous acid, 23 669 Dithiopolyesters, 23 739 Dithiozone extraction method, silver analysis via, 22 651 Dithizone, molecular formula, 5 713t Ditins, 24 826... 

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. 

Palladium-catalyzed intramolecular cross-coupling reaction of bis-aryl halides using ditin reagents. 

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). 

Fig. 9.1 Determination of the number of electrons by controlled-current coulometry [2]. The case when 0.1 mmol of 2,3,5,6-tetraphenyl-l, 4-ditin in AN is electrolyzed at constant current (50 mA). The CV curves were measured, from left to right, after 0, 1, 2, 3, 4, 5 and 6 min, 0 1 2 3 4 5 6 7 respectively.

Hexamethyl ditin (hexamethyldistannane) [661-69-8] M 327.6, m 23.5°, b 85-88°/45mm, 182°/756mm, d 1.57. Wash with H2O and extract with C H, dry by filtering through powdered Na2SO4, remove on a rotary evaporator and fractionally dist the oily residue under vacuum (b 85-... 

Similarly, compounds containing metal-metal bonds are four-coordinated, except in the case of the 1,2-bis(dicarboxylato)ditin compounds, (RC02)R2SnSnR2(02CR), which have the structure (49) where the carboxylato groups span the tin-tin bond.388,389... 

Iodocarbonyls are excellent substrates for atom transfer cyclization, as shown by examples from our recent work in Scheme 29.19-129 When two carbonyl (or cyano) groups are present, bromides can also serve as radical precursors. Photolysis with 10% ditin usually provides excellent yields of kinetic products at high concentration, and alkene substituents often dictate the regioselectivity. The y-iodo ester products are particularly versatile for subsequent transformations, which can often be conducted in situ. Although tertiary iodine products sometimes go on to give lactones or alkenes, primary and secondary iodides can often be isolated if desired. The last example is particularly noteworthy the kinetic product from the cyclization presented in Scheme 27 is trapped, because bromine atom transfer is much more rapid that reverse cyclization. 

Baum, G. A., Considine, W. J. Organotin chemistry. IV. Reduction of hexaorgano-ditins with lithium aluminium hydride. J. Org. Chem. 29, 1267 (1964). 

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. 

Equimolar amounts of lithium diisopropylamide (LDA) and tin hydrides reacted in THF to form diisopropylamine and the corresponding stannyllithium (equation 12)27,28. In diethyl ether or hexane, an excess of tin hydride was required for complete reaction which leads to the ditin compound and lithium hydride (equation 13). 

It was shown that in equation 13 the formation of ditin proceeds from an intermediate hydrostannyllithium (equation 14)27. 

Compounds according to entries 1, nitrato-(triphenylarsineoxide)triphenyltin 2, isothiocyanato-(triphenylarsine-oxide)tribenzyltin 3, di2-coumarin-3-carboxylato)-(coumarin-3-carboxylato)hexaphenyltriphenylarsineoxide-ditin 4, ( i2 -1,2-bis( dipheny larsoryl)-ethane- 0, 0X )-bis(chlorotriphenyltin). 

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