Optimization of polystyrene-supported triphenylphosphine catalysts for aza-Morita–Baylis–Hillman reactions

Abstract

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Immobilization of Organic Catalysts: When, Why, and How

“…[47] It is interesting to note that these reactions proceeded better in THF than in many other solvents. This fact was related to the excellent swelling of the polymer in THF.…”

Rasta Resin–PPh3–NBniPr2 and its Use in One‐Pot Wittig Reaction Cascades

“…[6] In recent years, our research has focused on studying various polymers as supports for reagent and catalyst immobilization, [7] and much of this work has focused on the attachment of phosphines. [8][9][10] In the context of the Wittig reaction, we have reported the use of the rasta resin architecture as a platform for phosphine reagent immobilization, [11,12] and the use of rasta resin-PPh 3 (1, RR-PPh 3 , Figure 1) in one-pot Wittig reactions in which the necessary phosphorane reagent was formed in situ by mixing an alkyl halide, a phosphine, and a base together with the aldehyde substrate (Scheme 1). [13,14] In this work, we observed that placement of the phosphine reagent groups on the flexible and solventaccessible grafts of the polymer rather than in the relatively rigid heterogeneous core allowed for 1 to be a more efficient reagent than typical commercially available polystyrene-supported phosphines, in which the functional groups are located in the interior of a heterogeneous polymer bead.…”

Tandem One‐Pot Wittig/Reductive Aldol Reactions in which the Waste from One Process Catalyzes a Subsequent Reaction

“…While the Wittig reaction has been a workhorse for alkene synthesis since its discovery over half a century ago, [3,4] its deficiencies with regard to atom economy [5] and product purification are well known. [6] In relation to the latter point, we have been studying polymer-supported phosphines, [7][8][9] and have recently reported new phosphine-functionalized polystyrenes that can be used in one-pot Wittig reactions in which product isolation/purification is reduced to simple filtration and solvent removal operations. [10,11] The one-pot reactions studied involved in situ generation of the required phosphorane by mixing the polymer-supported phosphine reagent, an a-halo carbonyl compound, and an amine base, followed by a reaction with an aldehyde substrate.…”