Al-MCM-41 as a mild and ecofriendly catalyst for Michael addition of indole to α,β-unsaturated ketones

Green synthesis of heterocyclic alkenes using MCM 41 supported perchloric acid catalytic system: characterization and DFT studies

CONTEXT

In this work, a series of heterocyclic alkenes were prepared by the reaction of 2-hydroxy-1-naphthaldehyde with various heterocyclic active methylene compounds via Knoevenagel condensation reaction using mesoporous silica, MCM 41, supported perchloric acid as an efficient green catalytic system under solvent-free conditions. A comparative study of the conventional method vs the green method was also reported with the same raw materials. ¹H NMR, ¹³C NMR, IR, and mass spectroscopic techniques were used for the characterization of synthesized compounds.

METHODS

Computational study was performed for these compounds by applying density functional theory (DFT) at M06 functional and 6-311G (d,p) basis set to interpret the electronic structures and counter check the experimental findings. The frequency analysis with aforementioned levels of DFT was performed to confirm the stability associated with optimized geometries. The true minimum for the optimized geometries for 1, 2, and 3 was achieved as indicated by the absence of negative eigenvalues in all the calculated frequencies. Additionally, natural bond orbitals (NBOs) and nonlinear optical (NLO) properties were explored utilizing the aforementioned level and basis set combination via DFT, whereas the frontier molecular orbitals (FMOs) evaluation was done at time-dependent density functional theory TDDFT at M06/6-311G(d,p). The global reactivity parameters were also calculated using the FMO data. These computation-based outcomes were found in good agreement with the experimental findings.

Cooperative acid–base bifunctional ordered porous solids in sequential multi-step reactions: MOF vs. mesoporous silica

Two different catalytic platforms, MOF and mesoporous silica, were compared as porous support for basic amino groups to promote sequential multi-step reactions.

Chemoselective aza-Michael addition of indoles to 2-aroyl-1,3-diarylenones

A total of 20 examples of 2-[(1 H-indol-1-yl)(aryl)methyl]-1,3-diphenylpropane-1,3-diones were efficiently synthesized by the aza-Michael addition at the N1 position of indoles with 2-aroyl-1,3-diarylenones at room temperature in the presence of potassium hydroxide. The salient features of this protocol are no transition-metal catalysts, mild conditions, high chemoselectivity, high atom economy, high yields, and a simple work-up procedure.