Immobilized ring-closing metathesis

A solid-phase synthesis of furo[3,2-3]pyran derivatives utilizing highly functionalized sugar templates has been reported <2003JOC9406>. After incorporation of alkenes within the sugar template, such as compound 95, the solid support is introduced via formation of the acid amide. This immobilized system then allows a ruthenium-catalyzed ring-closing metathesis that leads to the formation of the fused oxacycles. 

An elegant traceless linker variation on the ring-closing metathesis strategy resulted in the preparation of the tetrahydroazepine 201 from the immobilized diene 200, although the yield of 201 was only moderate (Equation 26) <1998EJ02583>. 

A different approach has used a basic tagged ruthenium complex for facile recovery and immobilization using PS-S03H [161,162]. A chemically tagged catalyst was immobilized to the solid phase (37), and the catalyst was activated because of the ammonium ion s electron-withdrawing properties (Scheme 4.74). The catalyst was used for ring closing metathesis in a continuously recirculated system (5 mol% Ru)... 

Scheme 16.86. Ring closing metathesis utilizing an immobilized Grubbs catalyst.

Fig. 37 Scheme of photocurrent generation. A porphyrin antenna was grown from a SAM on a gold surface by self-complementary coordination followed by covalent immobilization by a ring-closing metathesis reaction... 

Scheme 10.4 Ring-closing metathesis over an immobilized Ru catalyst.

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