| Chromone and indole fragments are found in tremendous number of bioactive natural products and clinically used drug molecules.They are two privileged structures for the development of new pharmaceuticals.Therefore,we studied on the methods for the construction of several types of indole and chromone derivatives from 3-diazoindolin-2-imines using transition metal catalyst.The main contents and results are summarized below(1)We investigated the Rh(Ⅱ)-catalyzed reactions of 3-diazoindolin-2-imines with aromatic aldehydes and α,β-unsaturated aldehydes,repectively.In the presence of 2.5 mol%Rh2(HFD)4,3-diazoindolin-2-imines reacted with aromatic aldehydes to furnish(E)-2-(amino(aryl)methylene)indolin-3-ones.The reaction underwent a cascade rhodium carbene formation/formal[3+2]cycloaddition/ring-opening and rearrangement process.Broad substrate scope,mild reaction conditions,(E)-configuration selectivity,and high yields were observed.In the cases where 2-fluorobenzaldehyde was used as reaction component,the resulted products could be conveniently converted to chromeno[3,2-b]indol-11(OH)-ones by treating with NaH.Interestingly,the outcome of reaction between α,β-unsaturated aldehydes and 3-diazoindolin-2-imines under slightly modified reaction conditions was 2,3-dihydropyrano[3,2-b]indol-4(5H)-imines instead of 2-methyleneindolin-3-ones.A 6π-ERC may be involved in this cascade process according to proposed mechanism(2)The reactions between 3-diazoindolin-2-imines and o-hydroxyarylenaminones were investigated.Cu(OTf)2 was found to be the best catalyst to promote the reaction to furnish 3-indolyl-4H-chromen-4-ones in moderate to good yields with broad substrate scope.A copper carbene-trigged electrophilic cyclization mechanism is proposed for this process.Furthermore,several pyrido[2,3-b:6,5-b’]diindoles and one pyrazino[2,3-b:5.6-b’]diindole were also obtained as by-products in some cases and they were found to emit strong fluorescence.Pyrido[2,3-b:6,5-b’]diindoles exhibited solvent-dependent emission,while pyrazino[2,3-b:5,6-b’]diindole emitted strong luminescence with 25.6%quantum yield in cyclohexane.(3)The Cu(Ⅱ)-catalyzed electrophilic cyclization reactions of a-diazomalonate with o-hydroxyarylenaminones were also investigated.The reaction provided 2-hydroxy-2-(4-oxo-4H-chromen-3-yl)malonates.Based on the results of condition control experiment and H2O18 labeling experiment,a H2O-participated electrophilic cyclization mechanism for this transformation is proposed.(4)The cooper(Ⅰ)-catalyzed oxidative C-C coupling reactions of 2-(sulfonylamino)-3,3’-biindoles,previously prepared from 3-diazoindolin-2-imnes by Dr Yanpeng Xing in our group,with diethyl malonate or anilines were investigated.The regioselective C-C coupling at 3 position of the indole ring bearing a sulfonylamino group was observed,providing 3-(1,3-diethoxy-1,3-dioxopropan-2-yl)-3-(indol-3-yl)indolin-2-amines and 3-aryl-3-(indol-3-yl)indolin-2-amines,respectively.A possible mechanism for this reaction is proposed on the basis of control experiments.We tried to obtain an enatioselective reaction by using some chiral ligands with consideration of the formation of a chiral tertiary centre in this process.Unfortunately,no satisfactory result was obtained. |
