Organotin reaction medium

This reaction in water appears to be attractive and environmentally friendly, since we do not need to use toxic solvents. However, if the water-soluble organotin species can not be recovered completely from the water used as a reaction medium, it becomes more toxic and dangerous than Bu3SnH. 

The polymer support does not necessarily have to be insoluble in the reaction medium. Thus, Sieber et al. [67] used poly(ethyleneglycol) as a soluble polymer matrix an iodobenzoate moiety linked to the support was allowed to react with tributylphenyltin to determine optimum conditions ((Ph3P)2PdCl2 (10%)/LiCl (10equiv.)/DMF/80°C). Precipitation into ether allows the removal of side products, excess reagents, and organotin by-products, leaving the polymer, which is recovered in 99% yield. Similar work has been carried out in an aqueous medium [68]. 

The formation of rings with more than seven atoms has unfavorable rates because the addition step is often too slow to allow it to compete successfully with other pathways open to the radical intermediate. In stannane based chemistry for example, premature hydrogen abstraction from the organotin hydride is difficult to avoid. However, Baylis-Hillman adducts 111 derived from enantiopure 1-alkenyl (or alkynyl)-4-azetidinone-2-carbaldehydes are used for the stereoselective and divergent preparation of highly functionalized bicycles 112 and 113 fused to medium-sized heterocycles (Scheme 38) [80, 81]. The Baylis-Hillman reaction using nonracemic protected a-amino aldehydes has been attempted with limited success due to partial racemization of the chiral aldehyde by DABCO after... 

We have also initiated MUssbauer spectroscopic studies of photochemical reactions of inorganic and organometallic compounds (iron chelate complexes, iron carbonyl and organotin compounds) isolated in low temperature matrices. Such systems provide a complimentary approach to solid-phase photochemistry since the reaction mechanisms may be simplified by isolating the reactant molecules in inert matrices (light transmission through the reactant is also facilitated by diluting tlie colored reactant with a transparent medium). Furthermore, we have a hope for the possible outcome of such studies — their application to syntheses of novel species which may be unstable at ordinary temperatures, unless trapped in inert matrices. 

The allylation of aldehydes via organotin reagents displays a negative activation volume [76]. As a matter of fact, the allylation of benzaldehyde with diallyltin dibromide is accelerated by addition of water [77]. The reaction was extended to various aldehydes and ketones and to various allylic organotin dichlorides [78] or tet-raallyltin in acidic aqueous medium [79]. With scandium triflate as a catalyst, tet-... 

In their study of the reactions of organotin compounds, Gielen et al [Gi 62-72] divided the solvent effect into two factors. They showed that whereas in polar solvents (methanol, dimethyl sulphoxide, dimethylformamide, etc.) the reactivity is governed by the steric effects of the substituents on the organotin compound, in apolar solvents (carbon tetrachloride, chlorobenzene, cyclohexane, etc.) inductive effects of these same substituents are manifested. Hence, the reactivity sequence of organotin compounds substituted in various ways is controlled by the solvent. According to this concept, in a polar medium the solvent behaves as a nucleophilic catalyst. 

Since Pereyre and coworkers reported the catalytic activity of tributyltin alkoxide for transesterification reaction [87], organotin derivatives have been used for various kinds of organic transformations. Distannoxane compounds were found to play an important role in the reaction [88-90] and act as pure Lewis acid [91, 92]. Although the transesterification reactions proceeded by using low-molecular-weight catalyst in homogeneous medium, a serious drawback for the industrial processes is a removal of the toxic tin derivatives. In such cases the use of polymer-supported version... 

In the carbonyl allylation with allylic bromides mediated by tin(ll) halide, organotin(iv) compounds were generally postulated (Mukaiyama et al, 1980). Tin(ll) chloride in the acidic aqueous medium MeOCHjCHjOH/HjO/AcOH/HCl (Uneyama et al, 1986b) or tin(ll) chloride with Amberlyst 15 in THF/HjO (Talaga et al, 1990) served as the promotor in allylation reactions yielding a-methylene-y-lactones. 

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