Sugar-derived catalysts

The asymmetric Baylis-Hillman reaction of sugar-derived aldehydes as chiral electrophiles with an activated olefin in dioxane water (1 1) proceeded with 36-86% de and in good yields of the corresponding glycosides (Eq. 10.47).104 The use of chiral /V-mcthylprolinol as a chiral base catalyst for the Baylis-Hillman reaction of aromatic aldehydes with ethyl acrylate or methyl vinyl ketone gave the adducts in good yields with moderate-to-good enantioselectivities in l,4-dioxane water (1 1, vol/vol) under ambient conditions.105... 

Vinyl epoxides are highly useful synthetic intermediates. The epoxidation of dienes using Mn-salen type catalysts typically occurs at the civ-olefin. Epoxidations of dienes with sugar-derived dioxiranes have previously been reported to react at the trans-olefin of a diene. A new oxazolidinone-sugar dioxirane, 9, has been shown to epoxidize the civ-olefin of a diene <06AG(I)4475>. A variety of substitution on the diene is tolerated in the epoxidation, including aryl, alkyl and even an additional olefin. All of these substitutions provided moderate yields of the mono-epoxide with good enantioselectivity. 

Glycals can be transformed into 1,6-anhydro sugar derivatives by intramolecular cyclization in the presence of Lewis and Brpnsted acids, a reaction that has been termed the intramolecular Ferrier glycosylation.168 Sharma el al.169 showed that a montmorillonite clay-supported silver reagent can be an efficient catalyst for this transformation. The 1,6-anhydro-2,3-dehydro sugars obtained were then selectively dihydroxylated to furnish 1,6-anhydro saccharides. 

Yadav et al.110 employed montmorillonite KSF as a catalyst for the reaction of arylamines with 2-deoxy-D-eryf/tro-pentose. The reaction took place on the surface of the catalyst and proceeded with cyclization to afford sugar-derived chiral tetrahydro-quinolines in high yields and moderate diastereoselectivity. 

A. P. Rauter, F. Ramoa-Ribeiro, A. C. Fernandes, and J. A. Figueiredo, A new method of acetonation with the zeolite HY as catalyst. Synthesis of O-isopro-pylidene sugar derivatives, Tetrahedron, 51 (1995) 6529-6540. 

V. K. Rajput and B. Mukhopadhyay, Sulfuric acid immobilized on silica An effcient reusable catalyst for the synthesis of O-isopropylidene sugar derivatives, Tetrahedron Lett., 47 (2006) 5939-5941. 

Itaconic acids are reduced in very high enantiomeric excesses (>97%) with Rh-TangPhos catalysts 658 Itaconic acid is reduced in 99.5% ee with the sugar-derived ferrocenyl phosphine 123.659... 

Raney Nickel was also used as the catalyst for the reduction of nitro sugars to amino sugars by hydrogenation.87 Under these conditions, nitro sugar 127 was reduced to amino sugar derivative 128, without removal of the benzyl protecting group. Compound 128 was finally converted into azepane 129 (Scheme 39).88... 

SCHEME 7. Sugar-derived ketones as catalysts for asymmetric alkene epoxidation... 

With DIOP-Pd(0) or -Ni(0) complexes as catalysts, moderate optical yields of up to 35% have been observed (126). Norbomene is convertible to the exo nitrile with up to 40% ee when a BINAP-Pd(0) complex is used (Scheme 57) (127). Ni(0) complexes of sugar-derived 1,2-diol phosphinites catalyze highly selective asymmetric addition of hydrogen cyanide to vinylarenes (128). This method gives the 2-naphthalene-2-propionitrile precursors of nonsteroid anti-inflammatory agents in up to 85% ee and in high yield. 

Heteropolyacids are also active for the conversion of sugar derivatives (360). H XMi2O40 (X = P, Si, M = W, Mo) are much more active than conventional catalysts such as p-toluenesulfonic acid and ZnCl2 for nucleophilic substitution... 

Carbonized sugar derivatives are used as solid acid catalysts for the production of biodiesel fuel,349 and carbonized sucrose treated with ethylene and then pyro-lyzed provides materials used as hard-carbon anodes for lithium-ion batteries.439... 

Pennequin I, Mortreux A, Petit F, Mentech J, Thiriet B (1994) Telomerisation of conjugated diene with sugar (derivs.) - by a reaction in aq. soln. and in the presence of a palladium catalyst and a ligand. FR 2693188... 

Treatment of halides or sulfonates with hydride donors such as tetrabutylammonium borohydride,38 lithium aluminium hydride,39 lithium triethylborohydride46 or sodium borohydride generate deoxy sugar derivatives (Scheme 3.8c).41 When sodium borohydride is employed, a transition metal catalyst (PdCk or NiC-b) may be added. 

A number of cyclic and sugar-derived halo acetals 273 were subjected to radical 5-exo cyclizations catalyzed by a cobalt salen catalyst 274 with NaB H4 as the stoichiometric reductant but in the presence of air (entry 11) [321, 322]. Under these conditions, bicyclic oxygenated tetrahydrofurans 275a were obtained in 50-84% yield. Diastereomeric isomers 275b were isolated as the minor components. The yields were similar to those obtained with tributyltin hydride. The oxygen concentration proved to be important, since air gave better yields... 

Sugar derived enals like 2- and 3-formyl hex-1- and hex-2-enopyranosides have also been used for the cycloaddition with enol ethers in the presence of Eu(fod)3 as a catalyst with good yields and high selectivity [172]. 

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