by a new interaction between the metal center and the second endocyclic oxygen atom (Zn?O1 for II ?? TMC-?(R,re) and Zn?O2 for II ?? TMC-?(R,si)), i.e., the formation of II ?? TMC-?(R,re) from II ?? TMC-?(R,re) and II ?? TMC-?(R,si) from II ?? TMC-?(R,si) As for 7CC-?(R), this step is kinetically accessible with a low activation barrier of +3.5 and +6.0 kcal.mol ?1 with respect to II ?? TMC-?(R,re) and II ?? TMC-?(R,si). Also, the two intermediates II ?? TMC-?(R,re) and II ?? TMC-?(R,si), metal centre and the endocyclic oxygen atom ,
the two final IV ?? TMC-?(R) and IV ?? TMC-?(R) products can also be obtained through a ring-opening step followed by the concomitant decoordination of the carbonate ester arm. Detailed analysis of the activation barriers for these two steps from II ?? TMC-?(R,re) and II ?? TMC-?(R,si), shows similar results to those obtained above from II ?? TMC-?(R,re) and II ?? TMC-?(R,si). Thus, the two final products can result from any of the two possible pathways ,
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