Chemoselective Hydrogen Transfer Reduction of Unsaturated Ketones to Allylic Alcohols with Solid Zr and Hf Catalysts

Abstract

α,β‐Unsaturated ketones were reduced to allylic alcohols with high chemo‐ and diastereoselectivity, using Zr and Hf compounds heterogenised on mesoporous molecular sieves.

A new method for the chemoselective reduction of aldehydes and ketones using boron tri-isopropoxide, B(O i Pr)3: Comparison with boron tri-ethoxide, B(OEt)3

“…Selective hydrogenation of α,β-unsaturated aldehydes and ketones such as crotonaldehyde, cinnamaldehyde, citral, 2-cyclohexen-1-one, benzalacetone (trans-4-fenil-3-buten-2-on) to their corresponding α,β-unsaturated alcohols is highly desirable due to the corresponding allylic alcohols are useful as intermediates, pharmaceuticals, and as flavour chemicals. [30][31][32] But the bond energy of C=C bond is smaller (615 kcal/mol) than that of C=O bond (715 kcal/mol), so which makes the hydrogenation of C=O bond difficult. 28 In this instance, the selective reduction of C=O bond using boron alkoxides as catalyst will be promising process for perfumery industry.…”

Activity of B(OEt)3-MCM-41 catalyst in the MPV reduction of crotonaldehyde

“…Boron alkoxide-containing ordered mesoporous silica material was prepared by the grafting method. 4,5 Prior to grafting, the support (MCM-41) (2.0 g) was dried at 250 • C for 2 h. It was then added to a solution of (1.5 mL; 5.8 mmol) B(OEt) 3 (as a 70 wt% solution in ethanol) in dry hexane (25 mL). The suspension was stirred (750 rpm) for 4 h at room temperature.…”

“…Several 'Meerwein-Ponndorf-Verley (MPV)' reduction catalysts such as Al-alkoxides, B-alkoxides, Zr-alkoxides as well as Hf and Zr alkyl complexes have been anchored on MCM-41 or on amorphous SiO 2 in order to generate potential catalytic activity. [4][5][6][7][8][9] Thus, grafting of MCM-41materials with MPV reduction catalysts yields active Lewis acid sites on MCM-41 materials. 4,5,10 Reduction of carbonyl compounds by hydrogen transfer from an alcohol is known as the 'Meerwein-Ponndorf-Verley reaction' or 'MPV reaction' in organic chemistry and can be performed under mild conditions using Lewis acids as catalyst.…”

“…[4][5][6][7][8][9] Thus, grafting of MCM-41materials with MPV reduction catalysts yields active Lewis acid sites on MCM-41 materials. 4,5,10 Reduction of carbonyl compounds by hydrogen transfer from an alcohol is known as the 'Meerwein-Ponndorf-Verley reaction' or 'MPV reaction' in organic chemistry and can be performed under mild conditions using Lewis acids as catalyst. 11,12 The MPV reduction of carbonyl compounds is a highly selective reaction since only the carbonyl group coordinates with the Lewis acid centre, while the double bond remains unreacted.…”

Chemoselective Transfer Hydrogenation of Flavoring Unsaturated Carbonyl Compounds over Zr and Hf‐based Metal–Organic Frameworks

“…In the last few years, zirconium-based catalysts have been attracting interest in this regard. [15][16][17][18] Hydrous zirconia proved to be a good catalyst for the catalytic transfer hydrogenation (CTH) reaction of cinnamaldehyde and gave a yield of 78% cinnamyl alcohol. 15 Moreover, transformation could be achieved under flow conditions.…”