Organotin compounds with halides

Coupling of organotin compounds with halides in a carbon monoxide atmosphere leads to formation of ketones by incorporation of a carbonylation step. ... 

Organotin compounds with tin-sulfur bonds are useful for the transformations of alkyl halides to sulfides (eq (119)) [114], esters to thiolesters (eq (120)) [115], and acetals to monothioacetals (eq (121)) [116]. 

The stannylenes from either source will insert into the Sn- Sn, Sn-R, or Sn-H bonds of organotin compounds, and react with alkyl halides, disulfides, or peroxides as shown in the reaction scheme below, but only the stannylenes that are generated photolytically will react with carbonyl compounds, and it appears that the stannylenes may exist in two forms, perhaps related as singlet and triplet, or a com-plexed and uncomplexed species. 

In basic aqueous media, a kinetic study of the reaction between stannate(II) ions and alkyl halide shows that mono- and disubstituted organotin compounds are formed (Eq. 6.12a).27 The monosubstituted organotin compound is obtained after a nucleophilic substitution catalyzed by a complexation between the tin(II) and the halide atom. The disubstituted compound results from an electrophilic substitution coupled with a redox reaction on a complex between the monosubstituted organotin compound and the stannate(II) ion. Stannate(IV) ions prevent the synthesis of the disubstituted compound by complexation. Similarly, when allyl bromide and tin were stirred in D2O at 60° C, allyltin(II) bromide was formed first. This was followed by further reaction with another molecule of allyl bromide to give diallyltin(IV) dibromide (Eq. 6.12b).28... 

Organotin compounds R SnCl4- (R = alkyl, n = 1-4) were prepared by reaction of tin powder with alkyl halides in the presence of RaN[(CH2CH20)mCH2CH20R ]3-a (R = alkyl, aryl, arylalkyl, R = H, alkyl, aryl, a =0, 1, 2, m = 0-20). Iodine should... 

Conversion of the organotin chlorides into fluorides, bromides, or iodides is usually carried out with the sodium halide in acetone, and residual organotin compounds are often removed as the insoluble organotin fluorides. The fluorides can then be converted back into the bromides, chlorides, or iodides (and exchanges by other halides can be brought about with aqueous ammonium halides at room temperature).332 A 2 1 mixture (solid solution) of CsF and CsOH, mixed with silica gel, also provides a very convenient way of removing organotin halide byproducts from solution.333... 

The palladium-catalyzed coupling of aiyl and vinyl halides to organotin compounds, known as Stille coupling, is one of the most important catalytic methods of carbon-carbon bond formation. The reaction is generally conducted in polar organic solvents, such as dimethylformamide, with tertiary phosphine complexes of palladium, although phosphine-free complexes or simple Pd-salts are also frequently used as catalysts [8]. 

Stille coupling was also developed in tlie early 1980s and is similar to Suzuki coupling in its sequence. It is used to couple aryl or vinyl halides or triflates with organotin compounds via oxidative addition, transmetallation, and reductive elimination. The oxidative addition reaction has tlie same requirements and preferences as discussed earlier for tlie Heck and Suzuki reactions. The reductive elimination results in formation of tlie new carbon-carbon bond. The main difference is that tlie transmetallation reaction uses an organotin compound and occurs readily without the need for an oxygen base. Aryl, alkenyl, and alkyl stannanes are readily available. Usually only one of tlie groups on tin enters into... 

As organotin compounds (organostannanes) undergo smooth Pd-catalysed transmetallation, aryl halides react with a wide variety of aryl-, alkenyl- and alkylstannanes [139]. Coupling with allylstannane is the first example [140]. The reaction is called the Migita-Kosugi-Stille or Stille coupling. Aryl, alkenyl, allyl, alkynyl and benzyl... 

Reactions of trimethylstibine sulfide with alkylindium halides are quite different from those with organotin compounds described above (30). As shown in the following equation, reaction of R InX with (CH3)3SbS gives stibonium salts ... 

---