Carbene transfer agent, production

Fig- 2 Full synthetic sequence for the production of the carbene transfer agent, 6... 

Simplest among these is direct oxidative addition (Eq. 11.39), where the outcome can be complicated by subsequent reactions of the hydride formed in the oxidative addition step. Direct metallation can be assisted by weak bases such as acetate because agostic binding of C(2)-H makes it easier to deprotonate the imidazolium ion. A very useful method is the initial formation of a silver carbene 11.21 from Ag20, followed by transmetallation to give the final product (Eq. 11.50). NHC carboxylate 11.22 and its esters are also useful NHC transfer agents (Eq. 11.51). ... 

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