Science of Synthesis

Gandon, V.; Thorimbert, S.; Malacria, M., Science of Synthesis, (2009) 46, 216.

The outcome of iridium(I)-catalyzed reactions of enynes depends upon both the structure of the substrate and the nature of the catalyst; thus, cycloadditions or cycloisomerizations may occur giving cyclohexadienes (see Section ‌46.5.2.2.6‌) or 1,3-dienes. 1,6-Enynes ‌152‌, which have an alkyl group at the acetylenic carbon but no substituents on the alkene unit can be cycloisomerized to form (Z)- or (E)-1-alkylidene-2-methylenecycloalkanes ‌153‌; however, an additive, either a phosphine (dppf seems to be the best choice) or acetic acid, associated with the catalyst dichlorobis(cyclooctadiene)diiridium(I) [Ir2Cl2(cod)2] dramatically influences the stereochemical course of the reaction (‌Scheme 53‌).[‌78‌,‌140‌]

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References