Tetraalkylstannanes reactions

Tetraalkylstannanes with an a-halo substituent undergo a, fi-elimination in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU, 90), yielding vinylstannanes with predominant -configuration, as shown in reaction 17273. 

Tetraalkylstannanes with double bonds at allylic or more remote positions undergo cross-coupling with allylsilanes to yield dienes, as illustrated in reaction 47299. 

Tetraalkylstannanes with a /i-acyloxy group undergo highly stereospecific elimination to yield Z - or E -unsaturated products, depending on whether the organotin compound has erythro- or threo-configuration, as depicted in reactions 72 and 73, respectively324. 

Tetraalkylstannanes undergo transmetallation reactions leading to reactive intermediates that may be combined with electrophilic substrates, as shown, for example, in reaction 74325. 

Whereas aliphatic and aromatic thiols cleaved the C—Sn bond in tetraalkylstannanes to give trialkylorganylthiostannanes768,855, the analogous reaction in organosilicon chemistry is absolutely unusual. According to Seyferth789,818 (1957), the vinyl group was especially easy to cleave from tin atom by mercaptans. 

Second-order rate constants for the reaction of mercury(II) chloride with tetraalkylstannanes according to equation 28 ... 

Tetraalkylstannanes and phosphorus pentafluoride are commercially available. Commercial phosphorus pentafluoride contains a small amount of phosphoryl fluoride, but its presence does not hinder the exchange reaction or cause any subsequent difficulties in workup of the products. It may be removed if desired, however, by carefully fractionating the commercial sample through —112° (CS2 slush) and —196° traps. The former trap will retain the phosphoryl fluoride, whereas the pentafluoride will pass this trap and collect at —196°. The vapor pressure of phosphorus pentafluoride at —96° (toluene slush) is 335 mm. Hg the purity of the sample may be checked by comparison of its vapor pressure against this value. 

A slight modification of the above description is necessary if this reaction is to be used for the synthesis of other alkylfluoro-phosphoranes (CH3CH2PF4, CH2=CHPF4, n-CH3CH2CH2PF4). Because all other tetraalkylstannanes are not transferable in a vacuum system at 25°, they can be syringed into the reaction bulb before attachment to the vacuum lines. Care to use dry samples and equipment must be observed, however, since the presence of even small amounts of water will lead to formation of phosphoryl fluoride and silicon tetrafluoride. 

For the first time tetraiodostannane was used in the reaction with tetraalkylstannanes by Pope and Peachey in 1903. They demonstrated that heating Me4Sn with Snl4 at >100°C led to MesSnl and MeSnD. Pii4Sn did not react with SnD even at 240°C. 

That unactivated carbon-dn bonds could be oxidized direedy in a potentially useful synthetic way was demonstrated in 1964. Symmetrical tetraalkylstannanes reacted with chromic anhydride (CrOs) in acetic acid to yield aldehydes and acids depending on the conditions (equation 1). Using a large excess of oxidant (12-fold excess) and long reaction times (360 h at 20 C) a near quantitative yield of n-butanoic acid was obtained from Bu"4Sn. ... 

Most tetraalkylstannanes similarly usually react by Sh2 at a hydrogen centre, but alkyltin halides and similar derivatives react by an Sh2 process at the tin centre, for example reaction 3-3. These reactions are useful for generating specific alkyl radicals for ESR and similar studies,2 and are discussed in Section 5.3.6 and 11.4. Photoexcited carbonyl compounds react in the same way. 

In what might be regarded as a related reaction, tetramethylstannane reacts with tetrakis(trifhioromethyl)stannane to give the mixed tetraalkylstannanes.23... 

The search for different or specific electron transfer sensitizers continues. Tetramethyl pyromellitate has been shown to be a useful sensitizer for the photochemical reactions of a,P-unsaturated ketones with tetraalkylstannanes. ... 

---