Gold and platinum catalysis of enyne cycloisomerization

This account provides a comprehensive overview of the development of gold and platinum catalysis of the enyne cycloisomerization. The use of these soft, alkynophilic metals enables mild, chemo-selective and efficient transformations of a variety of readily available acyclic enynes to a wide range of synthetically useful carbocyclic and heterocyclic products. The review is organized according to diverse structural types of enynes that undergo skeletal cycloisomerizations. The account begins with an overview of transformations of primarily 1,6-enynes to 1-alkenylcyclopentenes, bicyclo[4.1.0]heptenes, methylenecycloalkenes, bicyclo[4.3.0]nonadienes and bicyclo[3.2.0]heptenes. This section is followed by the discussion of cycloisomerizations of 1,5-enynes, which enable a rapid access to a range of other cyclic products, including bicyclo[3.1.0]hexenes, cyclohexadienes, heterobicycloalkenes, methylenecyclopentenes, naphthalenes and methyleneindenes. In addition, the [3,3] rearrangement of 1,5-enynes provides efficient access to the corresponding allenes. The account concludes with an overview of the most recent studies on gold- and platinum-catalyzed cycloisomerizations of 1,4- and 1,3-enynes. Due to the rapidly increasing interest in this area during the past three to five years, we believe that this review provides a timely and comprehensive discussion of the development gold- and platinum-catalyzed cycloisomerization starting from the initial pioneering investigations to the latest advances in the field. A significant em phasis is placed on the mechanistic discussion of the observed manifolds of skeletal reorganizations.