Direct Anti-Markovnikov Addition of Water to Olefin To Synthesize Primary Alcohols: A Theoretical Study

Anti-Markovnikov
addition of water to olefins has been a long-standing
goal in catalysis. The [Rh­(COD)­(DPEphos)]+ complex was
found as a general and regioselective group 9 catalyst for intermolecular
hydroamination of alkenes. The reaction mechanism was adapted for
intermolecular hydration of alkenes catalyzed by a [Rh­(DPEphos)]+ catalyst and studied by DFT calculations. Olefin hydration
pathways were analyzed for anti-Markovnikov and Markovnikov regioselectivity.
On the basis of the DFT results, the operating mechanism can be summarized
as follows: styrene activation through nucleophilic attack by OHδ− of water to alkene with simultaneous Hδ+ transfer to the Rh; this is then followed by formation
of primary alcohol via reductive elimination. The competitive formation
of phenylethane was studied via a β-elimination pathway followed
by hydrogenation. The origin of the regioselectivity (Markovnikov
vs anti-Markovnikov) was analyzed by means of studying the molecular
orbitals, plus natural atomic charges, and shown to be primarily orbital-driven
rather than charge-driven.