Hydrostannolysis reaction

The synthesis of tristannanes and linear tetrastannanes can be achieved in a straightforward manner by employing the hydrostannolysis reaction and diorganotin dihydrides (26) and 1,1,2,2-tetraorganodistannanes (9) according to Eq. (8) 49). As shown, this methodology can be used to... 

In addition to the hydrostannolysis reaction, another procedure that has been used for the synthesis of tristannanes, such as compound 39, is through the reaction of the triorganotin anions, R3SnLi, with diorganotin dihalides according to Eq. (9) in Scheme 8. This method has also been... 

In recent years, these reactions have found an important place in organic synthesis. We will consider in this chapter only the reactions of radicals with tin hydrides, and the basic hydrostannolysis processes that depend on these reactions. Hydrostannation reactions are covered in Section 4.4, and the reactions of stannyl radicals with substrates R X in Section 20.1.3. The further use of organotin hydrides in organic synthesis, which depends largely on transformations of the radicals R " in hydrostannolysis reactions, or of the radicals R3SnXY" in hydrostannation reactions, are beyond the scope of this book, but have been extensively reviewed.2 64 66 104 107... 

These are polar reactions with the components polarised in the sense Sn0+-N° and M6+-X°. Different behaviour is observed in the reaction of the aminostannanes with tin hydrides in which the polarisation appears to be in the sense Sn5-H5+ (equation 16-40), and the products are the distannane and amine. These hydrostannolysis reactions of amino- and amido-stannanes provide an important route to Sn-Sn bonded compounds, and are discussed in Section 18.2.1.3. 

Sometimes the problem can be reduced by using the organotin compound as a catalyst rather than as a stoichiometric reagent. A familiar example is a hydrostannolysis reaction which can be carried out with a catalytic amount of tin hydride in the presence of a borohydride. 

When deprotection reactions of the Aloe group with a palladium catalyst and pseudometallic hydrides, namely tributyltin hydride, sodium borohydride, or phenylsUane, are performed in the presence of an acylating agent, the deprotected amino group is directly obtained in its acylated form.P This tandem deprotection-acylation reaction is believed to involve a concerted decarboxylative condensation of the initially formed pseudometallic carbamate with the acylating agent, as represented in Scheme 8 in the case of hydrostannolysis.t ... 

The reaction of EtjSnH with EtjZn results in decomposition with the formation of Zn metal, ethane, tetraethyltin, hexaethylditin and a polymerp The reaction of PhjSnH with EtjZn in pentane or benzene forms metallic Zn. However, when hydrostannolysis is carried out with preformed complexes of Et2Zn or with a complexing solvent, such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THE), or by using a preformed coordination complex of EtjZn with tetramethylethylenediamine (TMED) or bipy, the bis(triphenyltin)zinc complexes are obtained in high yields under mild conditions (—20° to 0°C)2 ... 

In 1962, Kuivila showed that the reaction of trialkyltin hydrides with alkyl halides (hydrostannolysis) (equation 1-6) was a radical chain reaction involving short-lived trialkyltin radicals, R3Sn, 12 and in 1964, Neumann showed that the reaction with non-polar alkenes and alkynes (hydrostannation) (equation 1-7) followed a similar mechanism,13, 14 and these reactions now provide the basis of a number of important organic synthetic methods. 

Reduction of the halides with a metal hydride such as lithium aluminium hydride, sodium borohydride, or poly(methylhydrosiloxane) gives the corresponding organotin hydrides These have an important place in organic synthesis for the reduction of halides to hydrides (hydrostannolysis) and the addition to alkenes and alkynes (hydrostannation), by radical chain reactions. Further reactions may intervene between the pairs of reactions shown in Equations (1.1.3) and (1.1.4), and (1.1.4) and (1.1.5), and these reactions are particularly useful for inducing ring-closure reactions. 

The most common way to get organotin-Mg compounds is from organotin hydrides with an organomagnesium-halide reagent. The 1 1 reaction of PhjSnH with EtBrMg NEtj in Et20 at —15 to 0°C results in selective hydrostannolysis of the Mg—C bond as evidenced by the quantitative formation of ethane ... 

Ort/io-metallated palladium complexes of azo and hydrazobenzene catalyze the reduction by H2 of nitroaromatics, alkenes, alkynes, and aromatic carbonyl compounds. A palladium-aryl or bond in the precursor complex is a requirement for catalytic activity. The ligands are themselves susceptible to reduction. The kinetics of the reaction under 1 atm H2 have been measured. Palladium(O) complexes catalyze the hydrostannolysis of allyl and allyloxy carbonyl groups. The reaction can be applied to the selective protection-deprotection of aminoacid derivatives see equation (9). Alkenyl cyclopropanes carrying electron-withdrawing substituents are selectively hydrogenolyzed by Pd(0)/PBu3 catalysts... 

There are numerous ways of forming bonds between two group 14 atoms. An important one, discussed above, involves the nucleophilic attack of a silyl anion on a silyl halide. Another method, called hydrostannolysis, involves condensation of a Sn-H bond and a Sn-NMe2 linkage, with the elimination of HNMe2. Th following reaction leads to a branched Sn4... 

Hydrostannolysis is usually a reaction in which the bond between alkyl (or aryl) group and halogen or sulfur is cleaved reductively by an organotin hydride. In particular, hydrostannolysis is available for the dehalogenation reaction of a halide as shown in eq. (10.12). This reduction usually occurs in a stepwise fashion, the... 

The other reaction is organostannolysis. Organostannoiysis is the reaction with organic groups in place of hydrogen of hydrostannolysis described in Section 10.4.2. The reaction is shown in eq. (10.22a). These types of reaction are an... 

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