Multistep Cascade Catalytic Reactions Employing Bifunctional Framework Compounds

NewMOF compounds, [Zn-2(SDBA)(3-ATZ)(2)]& BULL;solvent, I and II, with tetrahedralZn centers as Lewis acidic sites and the free amino groups of the3-amino triazole ligand as strong Lewis base centers were shown tobe effective in the conversion of benzaldehyde dimethyl acetal to1-(1,3-dinitropropan-2-yl) benzene through a 4-step cascade reaction,which proceeds via deacetalization (Lewis acid),Henry (Lewis base), and Michael (Lewis base) reactions. Multistep cascade reactions are important to achieveatom as wellas step economy over conventional synthesis. This approach, however,is limited due to the incompatibility of the available reactive centersin a catalyst. In the present study, new MOF compounds, [Zn-2(SDBA)(3-ATZ)(2)]& BULL;solvent, I and II, with tetrahedral Zn centers as good Lewis acidic sitesand the free amino group of the 3-amino triazole ligand as a strongLewis base center were shown to perform 4-step cascade/tandem reactionin a facile manner. Effective conversion of benzaldehyde dimethylacetal in the presence of excess nitromethane at 100 & DEG;C in waterto 1-(1,3-dinitropropan-2-yl) benzene was achieved in 10 h with yieldsof & SIM;95% (I) and & SIM;94% (II).This 4-step cascade reaction proceeds via deacetalization(Lewis acid), Henry (Lewis base), and Michael (Lewis base) reactions.The present work highlights the importance of spatially separatedfunctional groups in multistep tandem catalysis the examplesof which are not common.

Automated summary

NewMOF compounds [Zn-2(SDBA)(3-ATZ)(2)]& BULL;solvent I and II were found to effectively convert benzaldehyde dimethyl acetal to 1-(1,3-dinitropropan-2-yl)benzene through a 4-step cascade reaction. This reaction utilized the tetrahedral Zn centers of the MOF compounds as Lewis acidic sites and the free amino groups of the 3-amino triazole ligand as strong Lewis base centers. The importance of spatially separated functional groups in multistep tandem catalysis was highlighted.