Million-Fold Acceleration of a Diels−Alder Reaction due to Combined Lewis Acid and Micellar Catalysis in Water

Abstract

The effect of micelles of sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), dodecyl heptaoxyethylene ether (C 12 E 7 ), and copper and zinc didodecyl sulfate (M(DS) 2 ) on the Diels-Alder reaction of 3-(para-substituted phenyl)-1-(2-pyridyl)-2-propen-1-ones 1a-g, containing neutral, cationic, or anionic substituents, with cyclopentadiene (2) has been studied. In the absence of catalytically active transitionmetal ions, micelles invariably retard the reaction. This can be rationalized on the basis of different binding locations of the reaction partners in the micelle. These binding sites have been probed using solubilizateinduced aromatic shifts in the 1 H NMR spectrum of the surfactant and paramagnetic counterion-induced relaxation enhancements of the 1 H NMR signals of the solubilizate. In contrast to SDS, CTAB, and C 12 E 7 , Cu(DS) 2 micelles catalyze the Diels-Alder reaction between 1 and 2 with extremely high efficiency, leading to rate enhancements up to 1.8 × 10 6 compared to the uncatalyzed reaction in acetonitrile. This results primarily from the essentially complete complexation of 1 to the copper ions at the micellar surface. Analysis of substituent effects and endo/exo ratios of the Diels-Alder adducts indicates that the reaction experiences a waterlike environment.

Synthesis and Evaluation of Biological Activities of Some 2-Hydroxy-1-Naphthyl Bicyclo [2.2.1] Heptene-2-Yl-Methanones

“…1,2,8,9 Rideout and Breslow 10 have studied the cycloaddition reaction of ethylenic ketones and cyclopentadiene in an aqueous medium and they reported the reaction rate is greater than 700 times faster than in non-aqueous media. Many catalysts such as Lewis acids, 5 Bronsted acids, 6,11 asymmetric helical polymers, 12 Cu 2+ ion-mediated nanotubes 13 and Micellar-DNAs 8, [13][14][15][16][17][18] have been employed for the Diels-Alder [4+2] cycloaddition reaction of cyclopentadiene (diene) and (E)-chalcones (dienophiles).…”

Selective Oxidations on Recoverable Catalysts Assembled in Emulsions

“…One of the most general and efficient methods that can overcome this disadvantage is to use surfactants, which solubilize the reactants or form colloidal dispersion in reaction systems. The biphase systems thus obtained include phase-transfer catalysis [4][5][6][7][8], micellar catalysis [9][10], and microemulsion [11][12][13] or emulsion [14][15][16][17][18] according to the different reaction circumstances.…”

Efficient Catalysis of a Diels−Alder Reaction by Metallo-Vesicles in Aqueous Solution

“…1,2 Among these, surfactants with counterions acting as active catalysts form a special class. [3][4][5][6][7][8][9] Metallo-micelles have been reported as catalysts for several types of reactions. [3][4][5]8,9 Other examples include catalysis of DNA hydrolysis by cerium phosphate bilayers 10 and catalysis of aldol reactions by lanthanide dodecyl sulfate dispersions.…”

“…[3][4][5][6][7][8][9] Metallo-micelles have been reported as catalysts for several types of reactions. [3][4][5]8,9 Other examples include catalysis of DNA hydrolysis by cerium phosphate bilayers 10 and catalysis of aldol reactions by lanthanide dodecyl sulfate dispersions. 6,11 Herein, we report efficient catalysis of a Diels-Alder reaction by vesicles, composed of a phosphate surfactant, with copper(II) as the active counterion.…”

“…Previously, this reaction has been studied in different solvents, with particular emphasis on water, both uncatalyzed and catalyzed by transition metal ions, as well as in micellar media of Me-(DS) 2 (Me ) Ni 2+ , Cu 2+ ; DS ) di-n-dodecylsulfate). 9,18 The rate is significantly enhanced by using water as a solvent, as well as by using specific Lewis acid catalysts, and the combination leads to spectacular rate enhancements, even further increased by using metallo-micelles as Lewis acids. 9 In the present study, vesicles have been prepared from equimolar amounts of the sodium salt of 5,5-di-n-dodecyl-2-hydroxy-1,3,2-dioxaphosphorinan-2-one (NadDP) and CuCl 2 .…”