Fluorous tin reagents

Scheme 7.77 Radical cydizations using fluorous tin reagents.

Benzotrifluoride dissolves both organic substrates/products and fluorous tin reagent... 

D. P. Curran, Z. Luo, P. Degenkolb, Propylene Spaced Allyl Tin Reagents A New Class of Fluorous Tin Reagents for Allylations under Radical and Metal-Catalyzed Conditions , Bioorg. Med Chem. Lett. 1998, 8,2403. 

Stille couplings with fluorous tin reagents (e.g., ArSnR ) have the advantage of convenient separation of the side products. 

A large number of fluorous tin reagents for use in palladium-catalyzed Stille cross-coupling reactions with organic halides or triflates have been developed. Reaction times can be reduced to just a few minutes when conducted with microwave heating. Three-phase extraction between water (top), dichloromethane (middle), and perfluorohexanes (FC-72) (bottom) allow the coupled product to be isolated from the dichloromethane and the resulting fluorinated tin chloride to be recovered from the FC-72 phase and recycled (Scheme 5.8.8). 

The reactions involving fluorous tin reagents discussed above also require fluorous reaction solvents and/or extraction solvents. These solvents are expensive and hazardous to human health and to the environment. Preliminary investigations towards an easily contained alternative have involved a fluorous monolayer on silica (Figure 5.8.2). 

Fluorous tin reagents. A gen ->elow. These compounds have su Ph,P)PdCl2 with LiCl as an additive... 

Fluorous tin reagents A general method for the syntheis of the reagents is shown below. These compounds have successfully been applied in Stille coupling using iPhjPfPdClj with LiCl as an additive in DMF-THF at 80°. 

One early example of microwave-assisted fluorous synthesis involved palladium-catalyzed Stifle couplings of fluorous tin reagents with aryl halides or triflates (Scheme 16.59) [90]. The desired biaryl products were isolated in good yields and purity after a three-phase extraction. Similar results were also achieved by use of so-called F-21 fluorous tags (CFl2CFl2CioF2i) on the tin reagent [91]. 

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