Cyclization via Double and Multiple Carbopalladation Reactions

Synthesis of benzene, cyclohexadiene, along with other related six-membered rings via circular trimerization of three C = C and/or C = C bonds has long attracted attention of the synthetic chemists. In most cases, it is thermo- 

Selective synthesis of benzene derivatives via partially intramolecular cyclic carbopalladation is considerably more complex than the corresponding all-intramolecular processes. As it is generally difficult to specify the cascade-initiation point in the Type Ila cychzation process, it would generally be the least selective path. A priori, the most favorable might be the intra-inter cascade cychzation process (Type Ilb), since both the point of initiation and the queuing order between the two alkynes is sharply differentiated by the fact that one is intramolecular, while the other is intermolecular. Still, in- 

All-lntramolecular circular cascade via dumbbeir-mode cyclization 

Since this topic is discussed in detail elsewhere in this monograph, no further discussion is intended here. 

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