Synergy Between Ldh Nanosheets And Intercalated Amino Acids Promoting β-functionalization Of Aldehydes

Functionalization and transformation of carbonyl compounds play a very important role in organic synthesis.Comparing with the activation of the ipso-and a-carbons of carbonyl compounds,the activation of the inert β-carbons of saturated carbonyl compounds is metal free,and remains a challenge.In the direct β-functionalization of saturated carbonyl compounds,the organic small molecule catalysts are more green and remarkably enantioselective than organometal complexe catalysts,but stoichiometric,pollutional,and toxic oxidants are required.The use of green oxidant meets the development tendency of green chemistry.Herein,a heterogenetic asymmetric catalyst,using layered double hydroxides(LDHs)with non-noble and variable valency metal atom doped as support and catalytic α-amino acid anions intercalated as amine center,was employed in the direct β-functionalization of saturated carbonyl compounds.With green oxidant O2,the non-noble metal atom in the LDH layers changed from low valency to high valency,and the catalytic cycle was achieved.With LDH nanosheets serving as the giant and rigid substituent of a-amine acids,the enantioselectivity was improved.The main research contents and results include:1.The oxidizing non-noble metal atom(Ni,Co and Mn)and interlayer amine was modified,MgNiAl-Ser-LDHs can catalyze the asymmetric cross-coupling reaction of 3-phenylpropanal and nitromethane with a lower activity than that of MgAlFe-Ser-LDHs.Yet MgCoAl-Ser-LDHs and MgMnAl-Ser-LDHs were invalid in the reaction.The basicity of LDH nanosheets was further changed by modifying the non-oxidizing metal atom(Mg and Zn).With improved basicity,the catalytic activity was improved.2.By using the designed catalyst with oxidizing non-noble metal Fe atom doped into LDH nanosheets and L-proline anions intercalated in LDH layers,and using green oxidant O2 to replace pollutional oxidant DDQ,the asymmetric cross-coupling reaction of 3-phenylpropanal and nitromethane was achieved with 55%yield and 90%ee.Relating the oxidation active center of catalyst structure,the structure of the catalytic activity center and alkaline to aldehyde and nitromethane asymmetric asymmetric coupling reaction,we have done in-depth study of multiphase bifunctional catalyst coordination catalytic effect,which confirmed that the use of hydrotalcite layer board as amino acids of rigid giant substituent improve the asymmetric reaction selectivity.Alkaline of LDH nanosheets,at the same time can greatly improve the activity of the reaction.3.Through the study of in-situ reaction under different atmosphere,possible multiphase synergistic catalytic mechanism is given.Further to make a study of the universality of the reaction by synergistic catalyst,we expand the substrates and the reaction types.