Fluorous allyltin

Free-radical-mediated four-component coupling reactions are rare. However, when an allyltin-mediated radical carbonylation is conducted in the presence of electron-deficient alkenes, four-component coupling reactions take place efficiently to give good yields of p-functionalized <5,fi-unsaturated ketones [40]. The wide scope of this four-component coupling reaction is noteworthy Primary, secondary, and tertiary alkyl bromides and iodides can be used as well as aromatic and vinylic halides. A variety of electron-deficient alkenes, such as methyl vinyl ketone, ethyl acrylate, acrolein, acrylonitrile, and vinyl sulfone, can be used as the acyl radical trap (Scheme 6.23). Fluorous allyltin compounds can also be used in four-component coupling reactions [41]. 

The allylation of carbonyl compounds with allyltin reagents is still an active area of organotin chemistry from the methodological point of view, and also for synthetic applications. For completeness we should add several alternative techniques, such as the development of trifluoromethanesulphonic acid as a Bronsted acid catalyst for the allylation of aldehydes in water123, or the design of fluorous allyltin reagents for the platinum-catalysed allylation of aldehydes124. 

Allyltin reagents supported on polymer underwent free radical allylic transfer with a marked preference for electron-poor carbon radicals598. The fluorous method developed by Curran and coworkers has recently been successfully extended to four-component radical reactions using fluorinated allyltin reagents599. 

A multicomponent coupling involving fluorous allyltin reagents has been reported, and rapid Stifle couplings are completed employing aryltris(polylfluoroalkyl)stannanes with microwave irradiation. ... 

The same strategy was applied to radical cabonylation with fluorous allyltin reagents. Propylene-spaced fluorous allyltin reagents 22 were tested as mediators for radical carbonylations the four-components coupling reaction with RX, CO, alkenes and the fluorous allyltin produced the -functionalized i8-aUylated ketones 23 (Scheme 28). Diphasic workup (acetonitrile and FC-72) was successfully carried out to separate the products from the tin compounds. Comparison experiments... 

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