Cyclization reactions ring-closing olefin

Grubbs applied his ring-closing olefin metathesis reaction to the synthesis of (lS,5R)-44 as shown in Scheme 67 [99]. The key-step was the cyclization of A to give C. The unreacted anti-isomer B could be recovered and equilibrated to a mixture of A and B. 

The photoreaction of the cyanouracil (262) with cyclo-octene, hex-l-ene, and acetoxyethylene in acetonitrile yields the adducts (266a—c) and the rearranged adducts (267a—c). ° The reaction is proposed to occur by the addition of the olefin to the excited state of the uracil yielding the biradical (268). This biradical can either ring close to yield the cycloadduct (266) or else cyclize to form... 

Dienes can be cyclized in the ring-closing metathesis (RCM) reaction with concomitant formation of volatile olefin side products (usually ethylene) (Fig. 4.12). RCM has been used to make small- and medium-sized rings, including carbocy-... 

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