Dienes cyclopropanation

Alkenes act as nucleophiles with alkynes in the presence of gold catalysts. In the most simple version of the reaction, enynes are converted with gold complexes or salts, and in the absence of nucleophiles, into rearranged dienes, cyclopropanated carbocycles, and/or bicyclic cyclobutenes. Depending on the length of the tether and the nature of the substituents, the olefin attack to the alkyne occurs in an endo or an exo fashion (equation 33). Besides, substitution at the alkene plays an important role on the regioselectivity of the nucleophilic attack. ... 

Ar1Ar3CN2 Carbene Diene Cyclopropane Ratio (cisjtrans) Yield (%) Ref... 

Allenes, 1,3-dienes, cyclopropanes, cyclopropenes, and even acetylenes can also serve as the starting materials for 7r-allylpaUadium complexes. Some representative examples are given in Scheme 19. It is interesting to note that while sterically hindered t-BuC=CBu-t displaces the two ethylene ligands from [Pd(CH2=CH2)Cl2]2 to give the corresponding alkyne-Pd complex (Sect. B.ii, Table 5), sterically less hindered PhC=CBu-t reacts with the same Pd complex to generate a 7r-allylpalladium species (Scheme 19). ... 

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