Tin reactions

The mechanism by which tin flame retardants function has not been well defined, but evidence indicates tin functions in both the condensed and vapor phases. In formulations in which there is at least a 4-to-l mole ratio of halogen to tin, reactions similar to those of antimony and halogen are assumed to occur. Volatile stannic tetrahaUde may form and enter the flame to function much in the same manner as does antimony trihaUde. 

Certain 1,5 diazabicyclo[3 3 0]oct-2-enes can be transformed unexpectedly into 4//-5,5-dihydro-l, 2 diazepines on heating [209] 1,5-Dipoles formed on heating of l,5-diazabicyclo[3 3 0]oct-2-enes [210] can be trapped with olefins to give [3+2] cycloadducts At elevated temperatures, they undergo a [3+2] cycloreversion Tins reaction sequence offers a simple route to dienes with interesting substitution patterns, for example, 1,1 bis(trifluoromethyl)-l,3-butadiene [211] The [3+2] cycloadducts that arise from the reaction of the 1,5 dipoles with acetylenes undergo... 

Fig. 4.12 Reaction energies for the second nucleobase-cispla-tin reaction (Fig. 4.11). (A) Formation of GA complex and (B) formation of GG complex. 

Figure 7. Fluorous tin reactions with separation by solid-liquid extraction...

Lanthanide triflates, for allylic tin reactions, 9, 354 Laser beam heating, in metal vapor synthesis, 1, 224 Laser methods, in mechanistic studies, 1, 248 Laser photochemical vapor deposition, with organometallic complexes, 1, 259... 

In the case of germanium and tin, reactions such as (162) lead to the production of GeMe - or SnMejj-metal complexes, stabilized by electron donation from the Lewis base, tetrahydrofuran (315). 

Linear growth of the Cu6Sn5 layer in the copper-tin reaction couple... 

Even combined water or water of crystallisation may induce tins reaction. Sodium carbonate, Na2C03.10H2O, is a useful salt to employ, and the reaction takes place at a more moderate temperature.2... 

Now the oxide must be removed and this is best done with trivalent phosphorus compounds such as (MeO)3P or PCI3. The phosphorus atom detaches the oxygen atom in a single step to form the very stable P=0 double bond. In tins reaction the phosphorus atom is acting as both a nucleophile and an electrophile, but mainly as an electrophile since PCI3 is more reactive here than (MeO)3P. 

Potassium hydroxide causes no precipitation from rhodium trichloride solution in the cold, but on adding alcohol a brown precipitate of hydroxide is obtained. Tins reaction is characteristic for rhodium. 

The reaction of phenols with alkyl halides or dimethyl sulfate in the presence of alkali to combine with the acid liberated is, of course, well known. The following preparation2 is selected as an example of the variety of alkyl compounds that enter into tins reaction, it being, of course, possible to consider chloroacetic acid, CICHjCOjH, as a methyl halide in which one of the hydrogens has been replaced by a carboxyl group. 

Tins reaction is tiiely different from that observed with ethylene euiflde or oicetane. Jh the first atage, a derivative is formed... 

These mechanisms are discussed, together with the reactions, below. By most of these mechanisms, the alkyl-tin bond is less reactive than the aryl-, alkenyl-, alkynyl-, allyl-, or benzyl-tin bond, and when two types of group are bonded to tin, reactions are selective for this second class of group. 

When (R)-binaphtol 3.7 (R = H) is used as a titanium ligand, the catalytic asymmetric oxidation of arylmethylsulfides by fe/7-BuOOH in the presence of water in CCI4 leads to (i )-sulfbxides [815, 947, 1514], In tins reaction, the initial oxidation of the sulfide into the chiral sulfoxide takes place with a moderate ee (= 50%). This step is fbllowed by further oxidation of the sulfoxides with kinetic resolution ( 1.6) [815, 1514]. To observe a high enantiomeric excess (> 90%), it is necessary to oxidize the minor (S)-enantiomer into the corresponding sulfone, and the chemical yield of the sulfoxide is in the 45 - 65% range. 

The n-butyl bromide-tin reaction under gamma radiation yields DBTDB as the main product. 

For reasons that will be discussed in the next chapter (Section 11.16), tin reaction works best when applied to tertiary alcohols, R3COH. Primary aiu secondary alcohols also react, but at slower rates and at higher reactiot temperatures. Although this is not a problem in simple cases, more com plicated molecules are sometimes acid-sensitive and are destroyed by the reaction conditions. 

Mukaiyama aldol condensation (6. 590-591)/ Tins reaction can be effected in the absence of a Lewis acid catalyst under high pressure (10 kbar). Surprisingly the stereoselectivity is the reverse of that Of the TiClj-catalyzed reaction (equation I). The reaction can also be effected in water with the same stereoselectivity, but the yield is low because of hydrolysis of the sityl enol ether. Yields are improved by use of watcr-oxolane (1 1) and by sttnication. ... 

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