Allene cyclo-oligomerization

Alkynoic esters, 493-494 Alkynyldiethyl alanes, 144 Allene cyclo-oligomerization, 41 Allenes, 161,315-316,438 Allenic adds, 149-150 Allenic amides, 255... 

A brief kinetic study on the cyclo-oligomerization of allene with nickel(0) complexes has been reported. The rate of reaction increases in the order Ni -P(OPh)3 < Ni -PPha < Ni . Initial rates for pentamerization and tetramerization are first-order in allene concentration but the trimerization reaction is nearly zero order. The mechanisms illustrated in Scheme 4 are proposed. The complex [Ni(cod)js] produces complexes of allene trimer and tetramer below — 30 C but at higher temperatures the nickel(O) complexes catalyse the pentamerization reaction. In the presence of 1 to 2 mol of a phosphorus ligand only the trimer complex is formed. ... 

Metal-AUene Reactions.—Allene oligomerization with metal catalysts has been intensively studied recently. The phosphorus ligand in nickel(O) catalysts has a powerful controlling effect upon oligomerization of allene. Thus a nickel-(cyclo-octa-l,5-diene)2 complex combined with 1—4 moles of t-alkyl-or aryl-phosphine oligomerizes allene mainly to tetramer (364), whereas... 

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