Aldehydes amine-catalyzed system

S. Kobayashi, T. Busujima, S. Nagayama, Ln(OTf)3- or Cu(OTf)2-Catalyzed Mannich-Type Readions of Aldehydes, Amines, and Silyl Enolates in Micellar Systems. Facile Synthesis of (5-Amino Ketones and Esters in Water Synlett. 1999,545-546. 

Various alkane oxidations are catalyzed by iron complexes. Such reactions are important in view of the action of non-heme iron enzymes, such as methane monooxygenase, in hydrocarbon oxidations in biological systems. For example, the oxo-bridged complex [Fe2(TPA)2(ju,-0)(ju.-0Ac)]3+ [TPA = tris(2-pyridylmethyl)-amine] catalyzes the oxidation of cyclohexane with Bu OOH. Related complexes with an Fein2(/i-0)(/i-0Ac)2 core oxidize cyclohexane or adamantane to give a mixture of alcohols and ketones.159 Less well defined systems, e.g., FeCl3-6H20/ aldehyde/AcOH/02 are similarly active.160... 

In a related reaction, aqueous allylation of imines has been reported by Bel-luci and co-workers using allyltributylstannane under lanthanide triflate catalysis [130]. Alternatively, the reaction can be performed without catalysis directly with the formaldehyde-generated immonium salts in aqueous media to give, in excellent yields, bis-homoallylamines and tertiary homoallylamines with primary and secondary amines, respectively [131]. These homoallylic amines were also prepared by Sc(OTf)3-catalyzed three-component reactions of aldehydes, amines and allyltributylstannane in micellar systems [132]. 

While allylation of imines is also catalyzed by Sc(OTf)3 in dichloromethane to give homoallylic amines in moderate yield, three-component reactions of aldehydes, amines, and allyltribut-yltin proceed in micellar systems to afford the corresponding homoallylic amines in good to high yield (eq 12). It is suggested that imine formation from aldehydes and amines is very fast under these conditions, and that the selective activation of imines rather than aldehydes is achieved. Allylation of (V-benzoylhydrazone or three-component reaction of aldehydes, benzoylhydrazine, and tetraallyltin are also catalyzed by Sc(OTf)3. ... 

The Mannich and related reactions provide one of the most fundamental and useful methods for the synthesis of P-amino ketones or P-amino esters. Three-component Mannich-type reactions of aldehydes, amines, and silyl enol ethers have been developed. With the development of green solvent systems, this reaction was also examined in a fluorous phase using perfluorinated rare earth metal salts including Sc(0S02C8Fi7)3 [5]. A characteristic point of this system is that it can be reused many times without reloading a new catalyst. There are also many reports on other scandium-catalyzed Mannich reactions. For example, Sc(OTf)3 was found to be an efficient catalyst for the three-component Mannich-type reactions of aromatic aldehydes, ketones, and nitriles in the presence of acetyl chloride (Scheme 12.3) [6]. 

Kobayashi, S., Busujima, T. and Nagayama, S., Ln(OTf)3- or Cu(OTf)2-catalyzed Mannich-type reactions of aldehydes, amines, and silyl enolates in micellar systems. Facile synthesis of -amino ketones and esters in water, Synlett, 1999, 5, 54 546. 

Despite these mechanistic and theoretical studies, intermolecular amine-catalyzed aldolizations have only rarely been used on a preparative scale. A few note vorthy exceptions in vhich aldehydes are used as donors are sho vn in Scheme 4.6 [51-55]. These reactions are often performed neat or in the presence of small amounts of an organic solvent. The catalyst usually used is either a primary or secondary amine, a combination of an amine vith a carboxylic acid, or simply an amino acid. These catalyst systems have previously been used in the Knoevenagel condensation and it is apparent that synthetic amine-catalyzed aldolizations originate from Knoevenagel s chemistry [56]. 

Cd. Cadmium perchlorate was found to catalyze allylation reactions using allyltributyltin in aqueous media very efficiently.177 These cadmium-catalyzed allylation reactions are accelerated by ligands such as N, N, N, N", A -pentamethyldicthylcnetri amine or 2,9-dimethylphenanthroline (Eq. 8.75). This accelerated the catalytic system to give allylation products of various aldehydes and ketones in high yields. 

Although molybdenum and tungsten enzymes carry the name of a single substrate, they are often not as selective as this nomenclature suggests. Many of the enzymes process more than one substrate, both in vivo and in vitro. Several enzymes can function as both oxidases and reductases, for example, xanthine oxidases not only oxidize purines but can deoxygenate amine N-oxides [82]. There are also sets of enzymes that catalyze the same reaction but in opposite directions. These enzymes include aldehyde and formate oxidases/carboxylic acid reductase [31,75] and nitrate reductase/nitrite oxidase [83-87]. These complementary enzymes have considerable sequence homology, and the direction of the preferred catalytic reaction depends on the electrochemical reduction potentials of the redox partners that have evolved to couple the reactions to cellular redox systems and metabolic requirements. 

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