Thiourea electron deficient

Wittkopp and Schreiner introduced the simple electron-deficient N,N -bis [3,5-(trif-luoromethyl)phenyl]thiourea 9 (Figure 6.3) as an efficient double hydrogen-bonding organocatalyst in a series of Diels-Alder reactions and 1,3-dipolar cycloadditions of... 

Takemoto et al. discovered N-phosphinoyl-protected aldimines as suitable electrophilic substrates for the enantioselective aza-Henry [224] (nitro-Mannich) reaction [72] with nitromethane, when utilizing thiourea 12 (10mol%) as the catalyst in dichloromethane at room temperature [225]. The (S)-favored 1,2-addition of nitromethane to the electron-deficient C=N double bond allowed access to various P-aryl substituted N-phosphinoyl-protected adducts 1-5 in consistently moderate to good yields (72-87%) and moderate enantioselectivities (63-76%) as depicted in Scheme 6.73. Employing nitroethane under unchanged reaction conditions gave adduct 6 as a mixture of diastereomers (dr 73 27) at an ee value of 67% (83% yield) of the major isomer (Scheme 6.73). 

P-Amino carbonyl compounds containing an a-atkyUdene group are densely functionalized materials, which are widely applied in the synthesis of medicinal reagents and natural products [265]. These products are usually prepared through the classic aza-Morita-Baylis-Hillman reaction [176, 177] of activated imines and electron-deficient alkenes catalyzed by tertiary amines or phosphines. Chen and co-workers, in 2008, identified bis-thiourea 106 as a suitable catalyst for the... 

In the presence of thiourea 121 (20mol% in toluene at 4°C/20°C), the aza-Michael addition [149-152] of 0-benzylhyroxylamine to numerous frans-chalcones bearing electron-rich and electron-deficient (hetero)aromahc subshtuents as well as aliphatic side chains provided the respective P-keto hydroxylamines 1-8 in moderate to very good yields (35-94%) and low to moderate (30-60%) ee values... 

Electron-deficient oxazoline thiourea 222 turned out to be the most effective catalyst concerning activity (93% yield/48h/THF) and asymmetric induction (88% ee/rt) in contrast to 218-221, which gave poor results (Figure 6.62). The solvent screening revealed aprotic THF to be the solvent of choice, while polar prohc... 

With sulfur and triethylamine in dimethylformamide, compounds (86) give (89) (Equation (21)) <89JPR243>. With thiols or KjS, sulfides are produced (e.g., (90) and (91)), which show spasmolytic activity in vitro <86MI 404-01 >. Smooth 5N2-displacements of chlorine occur with phenol, thiophenol, SCN, and thiourea in dimethylsulfoxide. However, with K2CO3 or sodium cyanide, (86) (Ar = Ph) affords the trimers (92) or (93) (Scheme 32). With electron-deficient trans alkenes, stereoselective formation of cyclopropanes (94) was observed (Scheme 32). No reactions occur with maleates <66HCA412>. 

Compound 18 showed a remarkable color change from orange to brown (Amax=670 nm) in DMSO upon adding F". Color changes are most probably due to a charge-transfer process and electron-rich formation of hydrogen bonds between thiourea-bound F and the electron-deficient anthraquinone moiety. The anion was believed to form a 2 1 anion-to-ligand ratio as shown in Fig. 4. 

Later, a dramatic jump in the ee values was achieved by the same research group by introducing the thiourea moiety at the 6 -position of 44 [22]. Using 10 mol% of the quinidine-derived catalyst 46, the highly enantioselective Henry reaction between nitromethane and the aromatic aldehydes (electron-rich, electron-deficient, and... 

Irradiation of the thiopyran derivative (292a) results in extrusion of HNCS and the formation of the pyridine (292b, 63.3%) as the major product. The photochemical reactivity of the pyranthione (293) is concentration dependent in 3-methylpentane as solvent. At low concentrations the thione reacts with the solvent but at higher concentrations the main reaction is the production of thiyl radicals. Laser flash photolysis has been used to identify that the triplet excited state of (294) is involved in addition reactions which occur to electron deficient alkenes such as acrylonitrile giving (295), for example. Other compounds related to thiourea are also photochemically reactive. Thus the photochemical cyclisation of (296) to afford (297) has been reported. ... 

Asymmetric 1,3-dipolar cycloaddition reactions have been reviewed, but ongoing research is still vigorous. The effectiveness of 138, a phosphine modified from serine, for synthesizing cyclopentenecarboxylic esters from 2,3-alkadienoic esters and electron-deficient alkenes has been validated.Phosphine-thiourea 139 is useful for directing enan-tioselective combination of allenes and imines. ... 

Pfeifer and co-workers have described the use of a highly rigid[3]poly-norbornane as a scaffold on which to append electron-deficient thiourea subunits [39]. 

The formation of several 2-aminobenzothiazoles via palladium-catalyzed, direct intramolecular oxidative C-H functionalization was recently demonstrated by Batey at the University of Toronto. The substrates used were A -aryl thioureas which in the presence of an interesting co-catalytic Pd(PPh3)4/Mn02 system under oxygen atmosphere, yielded the desired products. In terms of the mechanism, this transformation proceeded presumably through electrophilic palladation, suggested by the higher reactivity of the more electron-deficient substrates. 

Several organocatalytic variants for the conjugate addition of electron-rich aromatic substrates to electron-deficient olefins have been reported in the last few years which apply the concept of activation of the electrophile by hydrogen-bonding interactions. In this context, chiral bifunctional thiourea ent-91 has been employed as an excellent promoter for the enantioselective conjugate... 

Benzoate salt of the vicinal diamine (249) has been found to catalyse a domino reaction of enones R CH=CHCOR with R CH=CHCOR that affords cyclic products containing three to four contiguous stereocentres (with 92-99% ee and >30 1 dr) " The self-assembly of proline and cinchona alkaloid-derived thioureas has been reported to dramatically improve the enantioselectivity of the inverse-electron-demand hetero-Diels-Alder reactions between aldehydes R R CHCH=0 and electron-deficient enones R CH=CHCOR , affording (250) after subsequent oxidation with PCC. °... 

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