Primary-tertiary diamine catalysts

The aldol reaction of cyclic ketones and acetone with aromatic aldehydes were carried out in combination with triflic acid in water at 25°C [250]. Other chiral primary-tertiary diamine catalyst such as compound 167 (20 mol%) was used in combination with solid polyoxometalate acid support (6.67% mol) in the aldol reaction between dihydroxyacetone (149a) and aromatic aldehydes in NMP as solvent at 25°C to afford mainly iyn-aldol products in good yields (59-97%) and high diastereo- and enantioselectivities (78-99% de, 84-99% ee). The combination of catalyst 167 with triflic acid was used in the reaction of acyclic ketones and a-hydroxyketones 8 with aromatic aldehydes also with good results [251]. Simple chiral diamine 168 (10 mol%) in the presence of Iriflic acid (20 mol%) was applied as catalyst in the reaction between acetone and cyclohexanone with aromatic aldehydes in water at 25°C, giving aldol adducts 4 in low yields (15-58%) and moderate diastereo- and enantioselectivities (50-98% de, 45-93% ee) [252]. 

Lu and Jiang designed primary-tertiary diamine catalyst derived from L-serine for the reaction of glyoxylates with acetone (1) [153]. Their catalyst provides a useful level of selectivity, though the reactions are rather slow. Ca-symmetric bisprolina-mide 12 assures the efficient formation of hydroxy esters with high stereoselectivity for a broad range of aryl a-ketoesters and cyclohexyl-substituted derivatives [154]. P,7-Unsaturated a-ketoesters furnish the desired compounds in excellent yields and ee when a cinchona-based catalytic system was used [155]. 

Amino acid-derived primary-tertiary diamine catalysts have been used extensively in aldol reactions. Lu and Jiang [34] documented a direct asymmetric aldol reaction between acetone and a-ketoesters catalyzed by an L-serine-derived diamine 17. Sels et al. [35] found that several primary amino acid-based diamines (18) were efficient catalysts for the syn-aldol reaction of linear aliphatic ketones with aromatic aldehydes. Luo and Cheng utilized L-phenylalanine-derived diamine catalyst 15a for the enantioselective syn-aldol reaction of hydroxyl ketones with aromatic aldehydes [36]. Moreover, a highly enantioselective direct cross aldol reaction of alkyl aldehydes and aromatic aldehydes was realized in the presence of 15a (Scheme 3.8) [37]. Very recently, the same group also achieved a highly enantioselective cross-aldol reaction of acetaldehyde [38]. Da and coworkers [39] discovered that catalyst 22, in combination with 2,4-dinitrophenol, provided good activation for the direct asymmetric aldol reaction (Scheme 3.9). 

DFT calculations, focusing on the C-C bond forming steps, have been used to rationalize the high regio- and stereo-selectivities found for direct aldol reactions of aliphatic ketones (propanone, butanone, and cyclohexanone) with a chiral primary-tertiary diamine catalyst (trans-N,N-dimethy diaminocyclohexane). ... 

Inspired by the primary aminocatalytic motif in nature, our group is interested in developing simple and efficient chiral primary amine catalysts. With Hine s pioneering contribution as a starting point, we developed simple primary-tertiary diamine catalysts derived from chiral tran -cyclohexanediamine such as 24 for asymmetric aldol reaction with excellent efficiency and enantioselectivity. 

The use of an (5)-threonine/a,a-(5)-diphenylvalinol-derived ionic liquid 81 gave comparable results to the 0-iBu-L-tyrosine-catalyzed reaction, but the recovery of the catalyst was simpler [100]. The simple primary-tertiary diamine 38 proved syn-selective, though it works only for aromatic aldehydes [76]. For the synthesis of iy -aldols derived from active benzaldehydes, other catalysts bearing primary amine functionalities also gave satisfactory results [90b, 60, 100, 101]. 

Following the same iminium ion activation mode but with cinchona primary-tertiary diamine bifunctional catalyst 9, Chen and co-workers [108] described the asymmetric intramolecular aza-Michael addition of enone carbamates (Scheme 11.29). The reactions proceed in high yield and with good to excellent stereocontrol (up to 99% ee). 

Quite recently, chiral diamines have been recognized as effective catalysts in asymmetric catalysis [16]. Utilizing primary amino acid structural scaffolds, several novel diamine catalysts have been developed, which can be classified as primarysecondary diamines (12-14) and primary-tertiary diamines (15-18). Notably, such diamines are often used in combination with Bronsted acid additives for effective activation of substrates. 

Polyoxometalates (POMs) are transition metal oxygen clusters with well-defined atomic coordination structures. POMs are used as functional nano-colloidal materials and also as supports for catalysts via ion-pair interactions due to their acidic properties. Combinations of chiral diamines and POM 225 effectively catalyze enamine-based aldol reactions. Less than 1 mol% of chiral amine loading is suf-ficientto catalyze the reaction (Table 28.10, entries 1 and 2) [114]. Highly diastereo-and enantioselective cross-aldol reactions of aldehydes are accomplished using chiral diamine-POM 226 under emulsion conditions (entries 3 and 4) [115]. Sul-fonated polystyrene or fluoropolymer Nafion NR50 are also good supports for the immobilization of primary-tertiary diamines. The catalyst 227 can be recovered by filtration and reused for at least four cycles with no loss of stereoselectivity (entries 5 and 6) [116]. 

Luo S, Xu H, Li J, Zhang L, Cheng JP. A simple primary-tertiary diamine-Brpnsted acid catalyst for asymmetric direct aldol reactions of linear aliphatic ketones. J. Am. Chem. Soc. 2007 129 3074 3075. 

The simple primary-tertiary diamine salts can be successfully applied in the aldol reactions of a-hydroxyketones with good activity and excellent stereoselectivity. Notably, the catalyst enabled the reaction of dihydroxyacetone (DHA), a versatile C3-building block in the chemical and enzymatic synthesis of carbonhydrates. By employing either free or protected DHA, syn- or anh-diols could be selectively formed with excellent enantioselectivity (Scheme 5.7). Since enantiomers of diamine 26 and 29 are readily available, this class of chiral primary amine catalysts thus functionally mimics four types of DHA aldolases in nature [17b]. Later, simple chiral primary-tertiary diamine 27 derived from amino acid was also found to be a viable catalyst for the iyn-selective aldol reactions of hydroxyacetone and free DHA (Scheme 5.7) [18]. 

Mesoporous silica functionalized by chiral primary-tertiary diamine/Bronsted acid conjugates was successfully synthesized by Xiaobing et al. Two functionalities of this material, that is, the chiral organofunctional group and the mesoporous support, provided the chiral enhancement in the asymmetric aldol reaction of acetone with various aldehydes. The catalyst exhibited good activity and enantioselectivity without loss of activity. Particularly, the catalytic activity of SBA-15 with an immobilized chiral organic group increased in enantiomeric excess value of the reaction product as compared with silica gel as the support [89]. 

The higher activity of primary amines in the reaction involving enones as Michael acceptors has also been extended to the use of different bifunctional catalysts (Scheme 3.19), which usually contain a primary amine functionality connected to a basic site by means of a chiral scaffold, as is the case in the use of 280 and 55. These diamine catalysts have been found to be excellent promoters of the Michael reaction of enones with cyclic 1,3-dicarbonyl compounds and malonates respectively, the tertiary amine basic site present at the catalyst structure being responsible for assisting in the deprotonation of the Michael donor in order to increase the concentration of the nucleophile species. In a different approach, bifunctional thiourea-primary amine catalyst 56a has also... 

TGA/FT-IR and DSC/FT-IR were utilized in this research to characterize an amine activated epoxy resin system. The specific system under study was a near-monomeric diglycidyl ether of Bisphenol A (2-di-[4-(2,3-epoxy-l-propoxy)-l-phenyljpropane) with an epoxy equivalent weight of 173. The curing agent was composed of a mixture of 10% tertiary amine catalyst and 90% primary cycloaliphatic diamine. Cured and uncured systems were analyzed using these hyphenated techniques. 

Both primary and secondary amines are to be avoided since they will react with the isocyanates. Triethylene diamine and dimethylethanolamine are commonly used tertiary amine catalysts. 

Formic acid forms esters with primary, secondary, and tertiary alcohols. The high acidity of formic acid makes use of the usual mineral acid catalysts unnecessary in simple esterifications (17). Formic acid reacts with most amines to form formylamino compounds. With certain diamines imida2ole formation occurs, a reaction that has synthetic utiHty (18) ... 

Isocyanates also react with primary and secondary amine compounds. Tertiary amines cannot react with isocyanates because they do not contain active hydrogen atoms, but they are powerful catalysts for many other isocyanate reactions. Diamines are frequently used as chain extenders and curing agents in PU manufacture. The addition of a diamine to the reaction mixture increases the overall reactivity during polymerization. The reaction between an isocyanate group and an amine results in the formation of a urea bond. The polyurea segments present in the finished PU serve to increase the potential for both covalent and hydrogen bond crosslinks within the polymer. 

A catalyst of diisobutylene hydroformylation was synthesized by interaction of Rh2(CO)4Cl2 with nitrogen-containing polymer ligands obtained by treating chloromethylated copolymers of styrene and DVB with primary, secondary and tertiary amines [255]. The effect of diamine or substituted pyridine-type additions on the activity of carbonyl clusters of Rh was studied on RhgfCOIie during a... 

Bui The K, Concilio C, Porzi G (1981) Cyclization of alpha, omega aliphatic diamines and conversion of primary amines to symmetrical tertiary amines by a homogeneous ruthenium catalyst. J Org Chem 46(8) 1759-1760... 

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