Thiourea-amine

The best reactivity and selectivity was illustrated with the binaphthol derived thiourea amine catalyst 277. The substrate scope was explored primarily with P-aryl-nitro-olefms of both electron-donating and electron-withdrawing natures. Yields and selectivities were high for the majority of substrates (Scheme 78). 

The best enantioselectivity in the addition of C-nudeophiles to nitroolefins is that achieved by Takemoto et al. using the bifunctional thiourea-amine catalyst 55 (Scheme 4.26) [45]. 

These hosts include simple anion sensor systems containing urea, thiourea, amine, amide, alcohol, and pyrrole groups linked to chromophores. Chro-mophores used in this type of chromogenic anion sensors are mainly organic dyes such as azobenzene, nitrobenzene, indoaniline, and anthraquinone or... 

Scheme 2.42 The thiourea/amine catalyst-mediated addition of acyclic ketones to nitrostyrenes.

Table 6.2 Bifunctional thiourea-amine-catalyzed 1,4-additions to cyclic enones.

Table 6.11 Thiourea-amine-catalyzed Michael additions of 2,4-pentanedione.

Thiourea-Amine-Catalyzed Malononitrile Enolate Additions to a,/ -Unsaturated Imide [30] (pp. 196-197)... 

Thiourea-Amine-Catalyzed Michael Additions of 2,4-Pentanedione [31] (pp. 205-206)... 

Fig. 23.12 Homogeneous top) and PEG-immobilized bottom) versions of Miyabe s thiourea/ amine catalyst [32]...

The proposed polymerization pathway differs fundamentally from the coordination-insertion mechanism involving metal complexes, see Fig. 3.7 [5, 38]. Indeed, the nucleophilic catalyst only activates the monomer toward ring opening, whereas the metal complex activates the monomer, initiates the polymerization, and remains bound to the growing chain. The polymerization mechanism of a superbase or thiourea-amine catalyzed ROP will be discussed in more detail below. 

In 2003, Takanoto et al. reported the first highly enantioselective organocatalytic conjugate addition of 1,3-dicarbonyl compounds to nitroolefins catalyzed by bifunctional thiourea-amine catalyst 142 (Fig. 2.15)[238]. After Takemoto s report a wide... 

Scheme 4.6 Mechanism involved in the polymerisation of trimethylene carbonate using bifunctional thiourea—amine catalyst in presence of an alcohol.

Moreover, a water-compatible proline-derived thiourea-amine bearing a hydrophobic camphor scaffold was evaluated as an organocatalyst for the aldolisation of cyclohexanone with para-nitrobenzaldehyde, affording the aldol product with an excellent yield, an enantioselectivity of 99% ee and an excellent u t/-diastereoselectivity (Scheme 2.25). The reaction was carried out in the... 

Scheme 2.25 TUdolisation of cyclohexanone catalysed by pyrrolidinyl-camphor thiourea-amine.

Figure 5.45. Diverse applicability of novel N-heterocyclic carbene, bifunctional thiourea amine, and superbase catalysts for the polymerization of strained heterocyclics. Reprint courtesy of International Business Machines Corporation, copyright 2009 International Business Machines Corporation.

Adsorption results from a wide variety of interactions between the adsorbing species and the electrode surface. In some cases, the driving force for adsorption h merely dislike of the adsorbate for the electrolyte solution phase (ci. ad sorption of neutral organic molecules at the gas-liquid interface). In other cases, adsorption results from electrostatic (c.g. the adsorption of ions on a surface of opposite charge) or chargenJipole interactions, (e.g- the adsorption of thiourea, amines, aromatic molecules). The strongest mteracdons result from formation of a covalent bond between the adsorbate and the surface, e.g. the reduction of proton on Pt ... 

Table 29.3 Bifunctional thiourea-amine catalyzed addition of nitromethane to N-Boc imines.

Figure 14.1 Thioureas, amidines and guanidine bases for ROP. (a) Thiourea-amine (b) l-cyclohexyi-3-(3,5-bistrifiuoromethylphenyi)thiourea (c) (-)-Sparteine (d) DBU (e) MTBD (f) TBD.

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