THEORETICAL-STUDIES OF HETEROATOM-DIRECTED CARBOMETALATION - ADDITION OF MECU, ME2CU-, AND MELI TO SUBSTITUTED ACETYLENES

Ab initio theoretical studies of the additions of MeCu, Me2Cu-, and MeLi to acetylenes bearing heteroatoms substituents (i.e., OH and SH as well as SiH3, CH3, and H) have shown that the calculated and experimental regioselectivities of carbometalation reactions show excellent correlation, indicating that the activation enthalpy plays a decisive role in the regioselection of heteroatom-directed carbometalations. Energy decomposition analysis of the regioisomeric transition states for the MeCu and MeLi additions to the OH- and SH-substituted acetylenes indicates that electrostatic interaction is a dominant contributor to the energy difference between the regioisomeric transition states. On the other hand, the overall interaction energy is dependent on orbital and electrostatic interactions for the MeCu and MeLi additions, respectively.