Benzimidazole‐pyrrolidine/H⁺ (BIP/H⁺), a Highly Reactive Organocatalyst for Asymmetric Processes.

Abstract

The new chiral BIP catalyst exhibits excellent activities in amino-catalyzed aldol reactions when combined with an equimolar amount of a Broensted acid. The system is also examined in Robinson anellation and α-amination processes. -(LACOSTE, E.; VAIQUE, E.; BERLANDE, M.; PIANET, I.; VINCENT* JEAN-MARC; LANDAIS, Y.; Eur.

Proline-Catalysed Amination Reactions in Cyclic Carbonate Solvents

“…Dibenzyl (R)-1-(2-oxocyclohexyl)hydrazine-1,2-dicarboxylate ( 10a ) [ 66 ]. Obtained as a colourless oil (0.28 g, 71%).…”

“…Obtained as a colourless oil (0.28 g, 71%). ν max (neat) 3271 br, 2965 s, 1797 s, 1743 s and 1679 cm −1 m; [α] D 20 -21.0 (c = 0.1, CH 2 Cl 2 ) (lit [ 66 ]. [α] D 20 -24.1 (c=0.1, CH 2 Cl 2 )); δ H 1.6–2.5 (8H, m, (CH 2 ) 4 ), 5.1-5.2 (5H, m, 2 × CH 2 Ph and NCH), 6.88 (1H, br, NH), 7.3–7.5 (10H, m, ArH); δ C (75 MHz) 24.4 (CH 2 ), 26.7 (CH 2 ), 30.8 (CH 2 ), 41.2 (CH 2 ), 66.5 (2 × OCH 2 Ph), 67.9 (NCH), 127.7 (ArCH), 128.0 (ArCH), 128.1 (ArCH), 128.2 (ArCH), 128.5 (2 × ArCH), 135.9 (2 × ArC), 156.3 (2 × NCO 2 ), 206.9 (CO); HPLC (Chiralpak OD-H using hexane: i PrOH (90:10) as solvent at a flow rate of 0.9 mL/min) retention times 16.9 (minor) and 22.6 (major) minutes.…”

“… a) ee and absolute configuration obtained by chiral HPLC [ 66 , 67 ]. b) ee obtained by chiral HPLC, absolute configuration assigned by analogy with product 10a .…”

Catalytic Enantioselective Desymmetrization Reactions to All-Carbon Quaternary Stereocenters

“…Therefore, much effort has gone into the development of new chiral bifunctional enamine catalysts to improve the efficiency of this important desymmetric reaction. Some notable catalysts are shown in Scheme 4, including βamino acid cispentacin 17, 31 N-substituted bimorpholine derivatives 18, 32 benzimidazole pyrrolidine 19, 33 prolinamide 20, 34 proline-based tripeptide 21, 35 multifunctional N-tosyl-(S)binam-L-prolinamide 22, 36 L-prolinethioamide 23, 37 1,2-cyclohexanediamine-derived primary amine 24, 38 and the trifluor- omethanesulfonic salt of a primary amine 25. 39,40 For a detailed introduction, see the good review by Moyano and Rios.…”

Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

“…The α-amination of cyclohexanone with DEAD or dibenzyl azodicarboxylate (DBAD) under L-azetidine-2-carboxylic acid ( 3 ) catalysis showed improved enantioselectivities of 88–90% [ 27 ]. The benzimidazole-pyrrolidine (BIP) catalyst 4 was comparable to L-proline in terms of enantioselectivity with cyclohexanone and 1-silacyclohexan-4-one as substrates [ 28 ]. In a comparison between the efficiency of L-proline ( 1 ) versus 4-silyloxyproline ( 5 ) in the α-amination of cyclohexanone and derivatives, the catalyst 5 provided higher yields and enantioselectivities than 1 [ 29 ].…”