Palladium zipper

The cycloisomerization reaction of dien- and oligoenynes has been developed by Trost and Shi and shows its remarkable potential by the palladium zipper, which has been used to create seven carbocychc rings in one step (Scheme 37). ... 

Scheme 11. Negishi s palladium-catalyzed zipper tetracyclization process.

Palladium(0)-catalysed coupling of non-conjugated dienes, aryl iodides and stabilized carbon nucleophiles has been developed468. An incredibly high yield (86%) of pentacycle 343 has been obtained from a Pd(0)-catalysed zipper reaction of acetylenic pentaene 342. The reaction is triggered off by a Pd-catalysed cyclization of acetylenic bond and the first olefinic bond469. 

Palladium-Catalyzed Cyclization via Carbopalladation and Acylpalladation Zipper"-mode cascade cylclization... 

Additionally, in what is termed a zipper cascade process, palladium-catalyzed reaction of 2-iodo-Af-tosylaniline (115), allenc and 2-iodothiophcne (116) provided the intermediate 117, which after cyclization was treated with boronic acids as capture reagents to provide the indolines 118 <01TL8677>. A similar approach was employed for the synthesis of spiro- and fused heterocycles <01CC964>. 

Scheme 8.69 A palladium-driven zipper-type sequential reaction [404].

It is noteworthy that, although Pd-catalyzed zipper mode cyclization under the Heck reaction conditions has widely been used for the construction of polycyclic systans, it would not be suitable for the construction of the capnellene skeleton with the cis-anti-cis stereochemistry, since the Heck reaction involves syn addition of an organopaUadium species to the carbon-carbon double bond followed by the syn elimination of a palladium hydride. Indeed, only the cis-syn-cis triquinane skeleton would be formed, and this has indeed been the case.f" ... 

A novel, three-component, palladium-catalyzed, cascade cyclization-anion-capture process which involves in situ generation of a zipper molecule has been reported. Thus, 2-iodobenzoyl chloride, an acetophenone imine, and carbon monoxide react in the presence of Pd(PPh3)2Cl2 to give isoindolin-l-one in moderate yield (eq 86). 

The combination of carbonylation with other reactions is one strategy often used to make a novel cascade reaction such as a zipper-type reaction [16], In the 1990s Negishi s group has reported a series of palladium-catalyzed cascade reactions involving carbonylation [17],... 

Finally, the intramolecular codimerization of C=C and C=C bonds under the influence of palladium catalysts have frequently been used for cyclization reactions. Although there is little firm mechanistic evidence for the reaction sequence involved, suitable design of the starting material has now allowed the simultaneous formation of up to five cyclopentane rings in a zipper-type reaction shown in Eq. (5). 

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