Uncatalyzed Knoevenagel Condensation in PEG-600 at Room Temperature

Abstract

A rapid, efficient, and ecofriendly protocol has been developed for the Knoevenagel condensation of active methylene compounds with aromatic, aliphatic, conjugated and heteroaromatic aldehydes in polyethylene glycol-600 (PEG-600) with good to excellent yields.

Expanded perlite: an inexpensive natural efficient heterogeneous catalyst for the green and highly accelerated solvent-free synthesis of 5-substituted-1H-tetrazoles using [bmim]N3 and nitriles

“…Therefore, replacement of environmentally hazardous catalysts with non-toxic, effectual and reusable catalysts that have been associated with great reactivity, operational simplicity and noncorrosive nature is highly desired. [1][2][3][4][5][6][7][8][9][10][11] On the other hand removing solvent from the reaction medium is a safety subject, while solvents are potentially toxic. Hence, utilizing the solventfree procedures is one of the proper options, particularly with respect to the E-factor.…”

Superacid Systems

“…Immobilization of fluoroboric acid (HBF 4 ) on silica was also successfully performed, 191,192 and the resulting material has shown good characteristics in catalytic transformations.…”

Perlite: an inexpensive natural support for heterogenization of HBF4

“…5,6 One approach to overcome the aforementioned problems is the replacement of environmentally hazardous Bronsted and Lewis acid catalysts with efficient and stable reusable solid acid catalysts that have been associated with high reactivity, operational simplicity, non-corrosive nature and the potential of the catalyst to be recyclable. [7][8][9][10][11][12][13][14][15][16][17] Perlite is a cheap mineral mixed oxide mixture which contains approximately 70-75% of SiO 2 and 12-18% of Al 2 O 3 (ref. 18) that can be used as a platform for the preparation of heterogeneous catalysts.…”