Cascade Reactions of 1,3-Enynes

2 CASCADE REACTIONS OF ALKYNES 4.2.1 Cascade Reactions of Enynes 

SCHEME 4.2 Mesomeric isomers of the initial intermediate of gold-catalyzed enyne cycloisomerization (for simplicity the tethering is omitted). 

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In 2003, Zhu and Zhang reported a palladium-catalyzed cyclization/arylation cascade reactions of enynes with arylboronic acids leading to cyclic products with a stereodefined exocyclic double bond [44] (Scheme 6.26). Several types of enynes can be anployed carbon, oxygen, and nitrogen tethers [Y=C(COjMe)j, O, Ts], and alkyl- and arylalkynes are well tolerated. The author proposed a plausible mechanism, probably involving a Jt-allylpalladium complex which is formed from the aUyUc halide, followed by insertion of the alkynes and Suzuki coupling reactions. 

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