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• 75-07-0 acetaldehyde 
• 105-07-7 4-cyanobenzaldehyde 

Relevant academic research and scientific papers

Enantioselective Aldol Addition of Acetaldehyde to Aromatic Aldehydes Catalyzed by Proline-Based Carboligases

Aromatic β-hydroxyaldehydes, 1,3-diols, and α,β-unsaturated aldehydes are valuable precursors to biologically active natural products and drug molecules. Herein we report the biocatalytic aldol condensation of acetaldehyde with various aromatic aldehydes to give a number of aromatic α,β-unsaturated aldehydes using a previously engineered variant of 4-oxalocrotonate tautomerase [4-OT(M45T/F50A)] as carboligase. Moreover, an efficient one-pot two-step chemoenzymatic route toward chiral aromatic 1,3-diols has been developed. This one-pot chemoenzymatic strategy successfully combined a highly enantioselective aldol addition step catalyzed by a proline-based carboligase [4-OT(M45T/F50A) or TAUT015] with a chemical reduction step to convert enzymatically prepared aromatic β-hydroxyaldehydes into the corresponding 1,3-diols with high optical purity (e.r. up to >99:1) and in good isolated yield (51-92%). These developed (chemo)enzymatic methodologies offer alternative synthetic choices to prepare a variety of important drug precursors.

Highly Enantioselective Cross-Aldol Reactions of Acetaldehyde Mediated by a Dual Catalytic System Operating under Site Isolation

Polystyrene-supported (PS) diarylprolinol catalysts 1 a (Ar=phenyl) and 1 b (Ar=3,5-bis(trifluoromethyl)phenyl) have been developed. Operating under site-isolation conditions, PS-1 a/1 b worked compatibly with PS-bound sulfonic acid catalyst 2 to promote deoligomerization of paraldehyde and subsequent cross-aldol reactions of the resulting acetaldehyde in one pot, affording aldol products in high yields with excellent enantioselectivities. The effect of water on the performance of the catalytic system has been studied and its optimal amount (0.5 equiv) has been determined. The dual catalytic system (1/2) allows repeated recycling and reuse (10 cycles). The potential of this methodology is demonstrated by a two-step synthesis of a phenoperidine analogue (68 % overall yield; 98 % ee) and by the preparation of highly enantioenriched 1,3-diols 4 and 3-methylamino-1-arylpropanols 5, key intermediates in the synthesis of a variety of druglike structures.

Organocatalytic direct asymmetric crossed-aldol reactions of acetaldehyde in aqueous media

A new type of diarylprolinol-based catalyst, which contains a dioctylamino group in the presence of a newly developed ionic liquid supported (ILS) benzoic acid as cocatalyst, is shown to be an effective catalytic system for the asymmetric direct crossed-aldol reaction of acetaldehyde in aqueous media using brine. For the reactions studied, the catalyst loading could be reduced to 5 mol %; high yields (up to 97%) and high enantioselectivities (up to 92% ee) were also achieved for a wide variety of aromatic aldehyde.

Chiral primary amine catalyzed asymmetric direct cross-aldol reaction of acetaldehyde

The first primary aminocatalytic direct cross-aldol reaction of acetaldehyde is presented. Among the various vicinal diamines screened, the L-tert-leucine derivative 1c in conjunction with (H4SiW 12O40)0.25 was identified as the optimal catalyst; good catalytic activity (up to 99% yield in 4 h), and high enantioselectivities (up to 92% ee) were achieved for a range of donors, including aromatic aldehydes and isatin derivatives. Aqueous acetaldehyde solution and paraldehyde can be conveniently applied in this system.