Tin dihydride

The successful conversion of 9 to 6 provided the original inspiration for the synthesis of the parent arsabenzene 2. The stannohydration of 1,4-pentadiyne 14 with dibutyl-tin dihydride furnished the necessary organotin precursor 1523). The exchange... 

The work on stannacycloalkanes and -cycloalkenes up to 1972 has been reviewed (9), and again, though in less detail, in 1982 (10). Most of the early studies concern the formation of five- and six-membered rings, and claims for smaller systems in particular should be treated with caution. More recent efforts have been directed to the synthesis of both strained and expanded rings. The synthetic methodology, however, remains dominated by the use of difunctional carbanion sources (Grignard and lithium reagents) or the hydrostannation reactions of tin dihydrides. 

One of the reactions that has been particularly useful in the generation of heterocyclic derivatives of Groups III and V is the exchange reaction with a tin heterocycle (normally derived by the direct reaction of a tin dihydride with a 1,3 diyne). The successful generation of Group V and III analogs of benzene relies on this synthetic route 11-13, 15) ... 

A PS-tin dihydride (68) reduced terephthaldehyde in 91% yield to an 86 14 mixture of monoalcohol and diol, as shown in Scheme 33. The selectivity can be attributed to limited mobility of the first-formed alkoxytin intermediate (69). 

In a modification of this method, the Sn-0 bonded compound can be generated in situ by partial acidolysis of a tin hydride, and, from the reaction between diphenyltin dihydride and carboxylic acids, a number of l,2-bis(acyloxy)-l,l,2,2-tetraphenylditins, (RC02)Ph2SnSnPh2(02CR) (e.g., R = CHj, CF3, PhaSi, or PhjGe), have been prepared (257, 258). 

Two effective tin reagents, triethylammonium triphenyltin and dibuthyltin dihydride have been offered for reduction of fused tetrazoloazines to aminoazines (87TL5941). The reaction was interpreted to proceed via ring opening to an azide and subsequent reduction. 

Hydrosilation of an alkenylsilane in the presence of a catalyst provides a route to five-, six- and seven-membered rings but is of little use for the smaller ones. Tin-substituted cyclohexa-2,5-dienes result directly from the a,[Pg.575]

An early example for the direct coupling of a tin reagent to Amberlite XE 305, a macroporous polystyrene, was reported by Crosby and coworkers157. The synthetic route is shown in Scheme 35. Reaction of the polymer-supported diorganotin dihydride 70 with iodooctane to give octane indicated a minimum content of 2 mmol tin hydride per gram of the polymer. 

J. T. Groves, S. Kittisopikul, Dehalogenation reactions catalyzed by tri-n-butyltin chloride. Competition for carbon radicals by borohydride and tin hydride, Tetrahedron Lett. 49 4291 (1977). N. M. Weinshenker, G. A. Crosby, and J. Y. Wong, Polymeric Reagents. IV. Synthesis and utilization of an insoluble polymeric organotin dihydride reagent, J. Org. Chem. 40 1966 (1975). 

Among the complexes which may function in this way are pentacyano-cobaltate ion, iron pentacarbonyl, the platinum-tin complex, and iridium and rhodium carbonyl phosphines. It has been suggested that with tristriphenylphosphine Rh(I) chloride, a dihydride is formed and that concerted addition of the two hydrogen atoms to the coordinated olefin occurs (16). There are few examples of the homogeneous reduction of other functional groups besides C=C, C=C, and C=C—C=C penta-cyanocobaltate incidentally is specific in reducing diolefins to monoolefins. 

The availability of diorganotin dihydrides from the reduction of the corresponding di-oxastannolanes12 renders alkylation of a lithium tin hydride an attractive route to other organotin hydrides with mixed organic groups, R2R SnH.35-36... 

In the air, the hydrides are oxidised to the corresponding hydroxides or oxides, presumably by a radical chain mechanism. The thermal stability of the hydrides R SnII4 increases as the value of n increases. Trialkyltin hydrides can be kept for long periods in the absence of oxygen, but dibutyltin dihydride is not stable enough to be commercially available. Decomposition is more rapid in the presence of a good ligand for tin, and this has been exploited in the formation of Sn-Sn bonds (see Section 15.3.4). 

A variety of synthetic methods employs tin hydrides as the starting materials. The interaction of triethyltin hydride with diethylmercury leads to hexaethylditin, mercury, and ethane 228). Hexamethylditin has been obtained by treatment of dimethyltin dihydride with sodium in liquid ammonia, followed by addition of methyl iodide. 

The versatility and selectivity of organotin hydride, is well documented. The use of polymeric organotin dihydride reagent involves ease of operation and reaction workup and avoids toxic vapours, characteristic of tin hydride. 

The method allows to obtain complexes, which polynuclear anions contain simultaneously organogermanium and -silicon- or -tin fragments. The interaction of Pr(OBu-t)3 with dihydrides (C6F5)2GeH2 or (QF5)2Ge(H)-Ge(H)(QF5)2 in the presence of [(C6F5)3Ge]2Hg leads to the complexes with 7- and 10-nuclear anions [18] ... 

Dimethyltin dihydride and an equal amoimt of tetrafluoroethylene UV-irradi-ated 20 hrs. at 50° dimethyl(tetrafluor thyl) tin hydride. Y 75%.—This is, ... 

The reaction was also carried out with functionally substituted phenyl isocyanates and with p-phenylene diisocyanate. The reaction of diethyltin dihydride with phenyl isocyanate affords a compound with two phenyl-formamido groups attached to one tin atom. 

The scope of this synthetic method was considerably enlarged when it was found (99) that 1 mole of a mono(iV-phenylformamido)tin compound reacts with 1 mole of a dialkyl- or diaryltin dihydride to give an organoditin monohydride. 

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