Investigation On Carbonylation Of Olefins&Regioselective Borylation Of Arenes

Aldehyde,ketone and carboxylic acid(ester)can be obtained directly by carbonylation of olefins.Synthetic gas(CO/H2)has been used as carbonyl source in industrial synthesis,mainly because of its convenience and low price.Usually the reaction needs to be carried out under high pressure,and the high quality of the reaction equipment is required.Although there are catalytic processes under low pressure,in general,the operation is inconvenient.Moreover,it is not convenient to study in the lab as a result of the toxicity and flammability of synthetic gas(CO/H2).In order to overcome the substantial drawbacks,scientists try to find new CO surrogates,so that the carbonylation of olefin can occur under safe,mild and convenient conditions.The carbonylation reaction which formate and formic acid serve as CO surrogate was studied in this paper.In addition,the mechanism of borylation of arenes C-H bond catalyzed by iridium was explored in detail.The main content of this article concludes three major parts as following:1.In our initial studies of Pd-catalyzed regioselective hydroesterification,2-(2-methylallyl)phenol was used as test substrate.The reaction was carried out in the presence of Pd(OAc)2 and DTBM-SEGPHOS using HCOOPh as CO surrogate and HCOOH as additive,seven-membered lactone formed with high selectivity under appropriate reaction conditions.Hydroesterification can be extended to various substituted 2-allylphenols,giving the corresponding seven-membered lactones in 62-93%yield.An asymmetric process was also investigated with(R)-(-)-DTBM-SEGPHOS,and 30%ee was obtained for the lactone.The reaction was also carried out with H13COOPh and H13COOH,respectively.The 13C was incorporated into the lactone when H13COOPh was used,indicating that the carbonyl group of the lactone was from HCOOPh but not from HCOOH.2.Styrene was used as the test substrate for our initial studies of Pd-catalyzed sequential carbonylation of olefins.The reaction was carried out in the presence of 2.5 mol%Pd(TFA)2 and 5 mol%dppp using HCOOH as CO surrogate,and ketone was obtained with moderate to good yield.The sequential carbonylation process can be applied to a variety of olefins,such as styrenes,acrylates and ethyl vinyl ketone,giving the corresponding ketones in 65-90%yields.While the cross carbonylation process between two different olefins was found to be generally less effective,unsymmetric ketones were isolated in moderate yields when the reaction was carried out with styrenes and excess of cyclohexene.The reaction was conducted with proper amount of HCOOH at lower temperature,giving ?,?-enones in good yield.Further studies showed that enone can be effectively reduced to ketone by HCOOH with or without Ac2O in the presence of the Pd catalyst.3.The mechanism of iridium catalyzed arenes meta-selective C-H borylation directed by hydrogen bond between ligand and substrate was studied.Experiments and DFT calculations indicate that the electronic effect of ligand has little influence on regioselectivity,however the steric effect of ligand and the borylation reagent has a significant effect.