Amphiphilic Immobilized Diphenylprolinol Alkyl Ether Catalyst on PS-PEG Resin

Abstract

Diphenylprolinol silyl ether is a widely used organocatalyst, and its immobilization on a solid support was investigated for the easy recycling and reuse of this catalyst. Because a silyl ether bond of the catalyst is weak, its alkyl ether was attached to polymers such as a polyquinoxaline-based polymer, a polystyrene polymer (PS) resin, and a polystyrene–poly(ethylene glycol) graft copolymer (PS-PEG) resin. Although a polymer-supported organocatalyst generally decreases its reactivity compared with the monomer catalyst, diphenylprolinol anthrylmethyl ether supported on PS-PEG was found to be a reactive organocatalyst; it catalyzed the Michael reaction of an aldehyde and a nitroalkene in water without an organic solvent being present, with excellent diastereo- and enantioselectivities.

Diastereoselective Synthesis and Functionalization of tert‐Butylsulfinyl‐2‐(Chlorodiphenylmethyl)Pyrrolidine

“…As last remark, the yet undisclosed amine ( R )‐ 2 m was tested as an organocatalyst in the benchmark Michael addition of aliphatic aldehydes 17 a and b to β‐nitrostyrene 18 (Scheme 5). In particular, propanal 17 a was reacted using the conditions reported by Hayashi in 2021 (5 mol% of catalyst, toluene as the solvent and p ‐nitrophenol as the additive), [8] while pentanal 17 b was used as reported by Ma in 2008 (1 mol% of catalyst, H 2 O as the solvent and benzoic acid as the additive) [19] . Amine 2 m proved to be a competent organocatalyst, affording the desired products 19 a and b in high yields and very good stereoselectivity (see Supporting Information for details).…”

“…Similarly to 5 , 6 also proved to be efficient only in some selected transformations. In 2021, Hayashi prepared a series of benzylic derivatives 7 (Figure 1, Ar=Ph; Ar’=Ph, 2‐naphthyl, anthryl) and tested them in the benchmark addition of aliphatic aldehydes to nitrostyrenes [8] . All members of this family proved to be more reactive than 1 (Figure 1, Ar=Ph; R 1 , R 2 , R 3 =CH 3 ), but less stereoselective.…”

Synthesis and Catalytic Activities of 3-Decyl-β-proline for Michael Reactions in Water without an Organic Solvent

“…Next, we conducted the reaction using several aldehydes and saturated aq KCl solution as the solvent (Table 2). 9 The use of aldehyde rather than cyclohexanone greatly shortened the reaction time. Although propanal gave a low yield, more lipophilic aldehyde gave high yields and high diastereoselectivities.…”

Asymmetric Flow Reactions Catalyzed by Immobilized Diphenylprolinol Alkyl Ether: Michael Reaction and Domino Reactions

“…[9] We also prepared an amphiphilic immobilized diphenylprolinol alkyl ether catalyst 2 on PS-PEG resin. [10] Flow reactions have attracted attention recently [11] because there are several advantages of flow reactions over normal batch reactions, such as improved heat-transfer, improved mass-transfer/mixing, improved reproducibility, and improved safety (managing hazardous reagents and intermediates). It also simplifies the process of conducting reactions under extreme reaction conditions such as high and low temperature, and high pressure.…”

“…For instance, diphenylprolinol silyl ether has been immobilized on solid supports by several groups [9] . We also prepared an amphiphilic immobilized diphenylprolinol alkyl ether catalyst 2 on PS‐PEG resin [10] …”