The ligand-dependent selectivities in Ullmann-type reactions of amino alcohols with iodobenzene by beta-diketone- and 1,10-phenanthroline-ligated Cu-I complexes were recently explained by the single-electron transfer and iodine atom transfer mechanisms (Jones, G. O.; Liu, P.; Houk, K. N.; Buchwald, S. L. J. Am. Chem. Soc. 2010, 132, 6205.). The present study shows that an alternative, oxidative addition/reductive elimination mechanism may also explain the selectivities. Calculations indicate that a Cu-I complex with a negatively charged beta-diketone ligand is electronically neutral, so that oxidative addition of Arl to a beta-diketone-ligated Cu-I prefers to occur (and occur readily) in the absence of the amino alcohol. Thus, coordination of the amino alcohol in its neutral form can only occur at the Cu-III stage where N-coordination is favored over O-coordination. The coordination step is the rate-limiting step and the outcome is that N-arylation is favored with the beta-diketone ligand. On the other hand, a Cu-I complex with a neutral 1,10-phenanthroline ligand is positively charged, so that oxidative addition of Arl to a 1,10-phenanthroline-ligated Cu-I has to get assistance from a deprotonated amino alcohol substrate. This causes oxidative addition to become the rate-limiting step in the 1,10-phenanthroline-mediated reaction. The immediate product of the oxidative addition step is found to undergo facile reductive elimination to provide the arylation product. Because O-coordination of a deprotonated amino alcohol is favored over N-coordination in the oxidative addition transition state, O-arylation is favored with the 1,10-phenanthroline ligand.