Synthesis, Characterization and Catalytic Properties of Chiral BINOL Functionalized Mesoporous Silicas for Enantioselective Morita-Baylis-Hillman Reaction

Abstract

Several Chiral BINOL functionalized mesoporous silicas were prepared by post grafting of organosilane derivatives of (S)-BINOL (1,1 0 -bi-2-naphthol) on SBA-15 and characterized by 13 C CP/MAS NMR, FT-IR, UV-visible absorption spectra, elemental analysis, powder XRD, nitrogen adsorption-desorption isotherms and TEM techniques. Their catalytic properties were demonstrated in enantioselective Morita-Baylis-Hillman reaction of 3-phenylpropanal and cyclohexenone. Among them, 3BSBA-15 linked through the 3 position of BINOL exhibit higher enantioselectivity (26% e.e.) and yield (88%) which are similar to the homogeneous catalyst (S)-BINOL (27% e.e. and 92% yield) as Brønsted acids catalyst, while complex of 3BSBA-15 and calcium 3BSBA-15-Ca show lower enantioselectivity (21% e.e.) than its homogeneous complex (S)-BINOL-Ca (32% e.e.) as ligand catalyst. 3BSBA-15 and 3BSBA-15-Ca can be reused with no significant decrease in enantioselectivity and yield.

Recyclable organocatalysts based on hybrid silicas

“…113 Based on this result, Gao has synthesized by post-grafting method several chiral BINOL functionalized amorphous silica and SBA-15 materials for the asymmetric Morita-Baylis-Hillman reaction of 3-phenylpropanal and cyclohexenone, achieving modest enantioselectivities (see M7a-b for significant example of functionalization, M7a gave the best results) ( Figure 3). 114…”

(R)‐BINOL‐6,6’‐bistriflone: Shortened Synthesis, Characterization, and Enantioselective Catalytic Applications

“…The trialkylphosphine‐catalyzed addition of cyclohexenone onto 3‐phenyl propanal was selected as a model reaction (Scheme 4). The expected secondary alcohol [17] was produced quantitatively, versus 5 % for the control reaction with the plain BINOL [56,57] . If this outcome illustrates a promising effect of ( R )‐6,6′‐Tf 2 ‐BINOL 1 as a hydrogen bond donor catalyst for this transformation, the enantiomeric excess remained <30 %.…”

“…Significant effort has focused on improving the transformation efficiency. The first example of a highly enantioselective asymmetric MBH reaction using a chiral Brønsted acid was reported by Schaus [56,57] …”

Functionalization of MCM-41 and SBA-1 with titanium(iv) (silyl)amides

“…[54][55][56][57] Despite their high impact on homogeneous catalysis, there are only a few examples of BINOL derivatives immobilized on inorganic supports. [58][59][60][61][62][63][64] We have previously explored the consecutive grafting of titanium alkoxide and amide complexes onto dehydrated MCM-48 to produce TiO x overlayers as catalysts for cyclohexene epoxidation. 65…”

“…7). 62 Fig. 7 DRIFT spectra of Ti(NMe 2 ) 4 @MCM-41 (2a), (R-H 2 BI-NOL)@Ti(NMe 2 ) 4 @MCM-41 (2b) and Ti(NMe 2 ) 2 (R-BINOL) (5) in the range of 400-4000 cm À1 (for the range of 1300-4000 cm À1 , see ESI †).…”