The {recently|lately|not too long ago} reported Rh(II)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an {attractive|appealing|desirable|eye-catching} {strategy|technique|method|approach|tactic} to prepare coumarin derivatives with {high|higher} site-selectivity. Motivated by the mechanistic ambiguity ({on the|around the} origin {of the|from the|in the|on the|with the|of your} site-selectivity {and the|and also the|as well as the|along with the|plus the} {details|particulars|specifics|information|facts} for lactonization {etc|and so on|and so forth}.), we {conducted|performed|carried out} a detailed mechanistic study {of the|from the|in the|on the|with the|of your} rhodium-catalyzed lactonization of 2-arylphenols with density functional theory (DFT) calculations. {The results|The outcomes} {suggest|recommend} that the reaction {occurs|happens} {via|by way of|through|by means of} the coordination exchange, C-H bond activation, carboxylation, protonation and lactonization {steps|actions|measures|methods}. The rate-determining step {is the|will be the|may be the|would be the|could be the|is definitely the} carboxylation step, in which CO2 favorably inserts {into the|in to the} Rh-C bond ({instead of|rather than|as opposed to|as an alternative to|in place of} the {more|much more|a lot more|far more|additional|extra} nucleophilic Rh-O bond). The protonation step {after|following|right after|soon after|immediately after|just after} carboxylation is {critical|crucial|vital|essential|important}, which {makes|tends to make} the subsequent CO2-assisted lactonization feasible. Interestingly, the corresponding pKa {value|worth} {of the|from the|in the|on the|with the|of your} base can reasonably predict the reaction {energy|power} barrier {of the|from the|in the|on the|with the|of your} C-H bond activation step. The calculations will {provide|offer|supply|give|present|deliver} insights and {suggestions|ideas|recommendations} for the {development|improvement} and advancement {of the|from the|in the|on the|with the|of your} subsequent C-H bond activation carboxylation reaction. 2,4-Dichloro-5-fluoro-6-methylpyrimidine structure 2-Ethynyl-1,1′-biphenyl Chemscene PMID:23613863
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