Household Infrared Technology as an Energy-Efficient Approach to Achieve C-Cπ Bond Construction Reactions

Abstract

We examined the ability of short-wave infrared (IR) light in the λ1.5-3.0 μm region of the infrared emission spectrum to accomplish C−Cπ bond construction reaction between π-excessive azaheteroaromatic and different carbonyl substrates supported on a bentonitic clay catalyst in solventless condition via a three-component condensation reaction. Preliminary studies show that the implementation of a domestic Flavor-Wave® oven fitted with a halogen heater lamp as a chemical reactor was as effective as the use of near IR light (λ1.1 μm) in fostering batch-wise organic reactions. Overall, this approach reveals its potential exploitation as an energy-efficient source to assemble biologically engaging (hetero)arenebisindolylmethanes framework, in the same way, that assure its sustainable development as for efficient generation of small libraries of molecules comparable to high-tech instrumentations performances.

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

“…In the same year, Luna-Mora and his research group published an unconventional approach for the synthesis of BIMs, making use of infrared technology, which is an underutilized tool in organic catalysis [ 211 ]. They specifically exploited the infrared irradiation (IR) zone of λ (1.5–3.0 μm) to attain the electrochemically excited species of the carbonyl group that is crucial for the formation of the C–C bond between aldehyde and indole.…”

“…Various substituted aromatic aldehydes and indoles managed to form the respective BIMs in satisfying yields, ranging from 60–96%, with electron-donating substituents elevating product conversion rates. Therefore, the mechanism of action of this protocol is based on the absorption of energy from the IR source, which fosters the formation of an excited complex that triggers a physisorption interaction with the BLAS leading to the initiation of the Friedel–Crafts alkylation [ 211 ].…”

Friedel–Crafts Alkylation of Indoles with Aldehydes/Ketones Catalyzed by Bromodiarylethene-Based Photoacid Generators

“…Brown powder; yield: 0.07 g (78%); mp 204-206 °C (Lit. 29 mp 148-152 °C). 1 H NMR (300 MHz, DMSO-d 6 ):  = 2.17 (s, 6 H, CH 3 ), 2.37 (s, 3 H, CH 3 ), 6.03 (s, 1 H, CH), 6.48 (d, J = 4.3 Hz, 1 H thiophene ), 6.59 (d, J = 4.4 Hz, 1 H thiophene ), 6.74 (t, J = 7.9 Hz, 2 H arom ), 6.91 (t, J = 7.5 Hz, 2 H arom ), 7.01 (d, J = 7.9 Hz, 2 H arom ), 7.23 (d, J = 8.0 Hz, 2 H arom ), 10.76 (s, 2 H, NH).…”