Diamine-based catalyst

Add (Nafion or molybdic add)- and base (diamine-based or guanidine residues)-catalyzed reactions in the same pot Sol-gel immobilization of both catalysts... 

Among the most active catalysts for the asymmetric transfer hydrogenation of prochiral ketones and imines to chiral alcohols and amines are arene-ruthenium(II) amino-alcohol (or primary/ secondary 1,2-diamine)-based systems, with an inorganic base as co-catalyst, developed by Noyori139-141 and further explored by others (Scheme 27).142-145... 

Keywords Asymmetric organocatalysis Bifunctional catalyst Brpnsted base Chiral scaffold Cinchona akaloid Cyclohexane-diamine Guanidine... 

Figure 6.11 Typical tridentate ligand structure incorporating a chiral amino alcohol and modified diamine-based tridentate ligand structure attached to the solid support for parallel catalyst library strategy.

Berkessel and co-workers synthesized a library of structurally diverse tertiary amine-functionalized catalyst candidates incorporating a chiral 1,2- or 1,4-diamine chiral backbone [231, 232, 246]. Structure-efficiency studies through sequential modification of the diamine backbone, the tertiary amine functionality, the (thio) urea N-substituents as well as of the amide substituent pattern, exemplarily illustrated a Jacobsen-type 1,2-diamine-based structure (figure 6.24), identified... 

A highly enantioselective Michael addition of 1,3-dicarbonyl compounds to nitroalkenes has been reported that employs a newly developed Ni(II)-(bis)diamine-based catalyst (174). The reaction scope includes substituted and unsubstituted malonates, /3-keto esters, and nitroalkenes bearing aromatic and aliphatic residues.202... 

Dendrimer-Fixed Chiral Diamine-Based Catalysts. 84... 

Dehydrogenative oxidation of secondary alcohols in the presence of acetone is the reverse process of transfer hydrogenation of ketones with 2-propanol [87b, 95b]. Kinetic resolution of racemic secondary alcohols is possible using this process with an appropriate chiral catalyst and suitable reaction conditions. As exemplified in Scheme 45, a variety of racemic aromatic or unsaturated alcohols can be effectively resolved in acetone with a diamine-based Ru(II) complex 42 or 50 [129]. Chiral alcohols with an excellent optical purity are recovered at about... 

However, the most employed half-sandwich complexes with chiral chelating ligands were reported by Noyori et who designed a new type of active and robust Ru(II) catalyst precursors based on complexes of monotosylated diamines. The structure of one of these catalyst precursors 3.21 was determined by X-ray analysis and showed that the metal has (R) configuration (see Figure 3.6). 

The basic reaction scheme for formulating urethane-based pseudo poly(amino acids) requires a reaction of a diisocyanate with a diol in the presence of stannous oc-toate as a catalyst. Depending on their properties, either the diol or the diisocyanate could serve as the hard segment (h) or soft segment (s) as reported in Table 12.4. Several poly(urethanes) also include a diol- or diamine-based chain extender to yield a higher molecular weight product. 

In 2012, the first polymer supported bifunctional primaiy amine-ureas were developed by Portnoy and coworkers. This heterogeneous catalytic system was tested in the Michael addition of acetone, cyclic ketones and aldehydes to aromatic nitro-olefins leading to activities and selectivities unprecedented for immobilised catalysts. Catalyst 41 based on (ll ,2f )-diphenylethylene-1,2-diamine and a L-valine spacer provided the Michael products in yields ranging from 23 to 99% and in high enantioselectivity (up to 99% enantiomeric excess) (Scheme 19.43). Unfortunately, recovery of the polymer-catalyst and reuse was only tested for 3 cycles, maintaining the high levels of enantioselectivity, but with a significant loss in the yield. 

Later, Melchiorre and coworkers accomplished a challenging direct vinylogous aldol reaction of 3-methyl-2-(yclohexen-l-one with a-keto esters utilising a bifunctional primary amine-thiourea. Catalyst 48 based on the (l/ ,2/ )Kiiphenylethylene-l,2-diamine backbone combined with benzoic acid as cocatalyst promoted the reaction by means of a concomitant activation of both reacting partners (see TS in Scheme 19.55), the ketone via dienamine catalysis and the ester via hydrogen-bonding interactions (Scheme 19.55). 

Inspired by the well-established principles in oxidation catalysis with heme complexes, Gomez et al. designed a new catalyst platform based on modifications at the well-known mep and mcp ligands (mcp = iVA -dimethyl-A[,A[ -bis (2-pyridylmethyl)-cyclohexane-1,2-diamine) by introducing bulky pinene groups at positions 4 and 5 of the pyridine rings [64]. By doing so, [Fe(OTf)2((5,5,R)-mcpp)], [Fe(OTf)2((/ ,/ ,/ )-mcpp)], and [Fe(OTf)2((/ )-mepp)] complexes were synthesized (Scheme 17). 

Three classes of catalysts have been studied for the asymmetric hydrogenation of imines. One class of catalyst is generated from late transition metal precursors and bisphosphines. These catalysts have typically been generated from rhodium and iridium precursors. A second class of catalyst is based on the chiral titanocene and zirconocene systems presented in the previous section on the asymmetric hydrogenation of unfunctionalized olefins. The third class of catalyst is used for the transfer hydrogenation of imines and consists of ruthenium or rhodium complexes containing diamine, amino tosylamide, or amino alcohol ligands. " ... 

Expanding on the results of Noyori s original computational work on the (pre)catalyst 2 based on an amino alcohol ligand, in the case of the seminal catalysts based on N-sulfonylated 1,2-diamine ligands, a C-H...n interaction is still thought to be the main origin of enantioselectivity for the... 

A route to regioisomeric benzisoxazole structures featuring a key copper-catalyzed C—O bond formation has been reported. In an intramolecular cyclization similar to that shown in Scheme 24.34 for benzoxazoles, benzisoxazoles such as 64 could be synthesized from Z-conflgured o-bromoacetophenone oximes under the action of a diamine-based copper catalyst (Scheme 24.36) [128]. A range of 3-methyl-l,2-benzisoxazoles were synthesized in good yields. 

A fluorous chiral organocatalyst (18) promotes the formation of the anti-Mol product (with up to 96% ee) on reaction between aromatic aldehydes with ketones in brine. The enantioselectivity achieved on promotion of aldol and Mannich reactions by another di-diamine-based catalyst (19) can be reversed by the addition of an achiral acid and is to be the subject of further mechanistic investigation. ... 

As an alternative, tin enolates are very useful in these additions. Usually they are prepared in situ from the amide using tin(II) trifluoromethanesulfonate and a base. They are subsequently reacted with an enone, catalyzed by a Lewis acid47-48 (see Table 3). With triinethylsilyl trifluoromethanesulfonate as a catalyst, in the presence of proline derived diamines anti-adducts are formed exclusively49 (see Section 1.5.2.4.3.1.). 

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