Thiourea substituted

Chemical antiozonants comprise the second general class of commercial antiozonants. Of the many compounds reported to be chemical antiozonants, nearly all contain nitrogen. Compound classes include derivatives of l,2-dihydro-2,2,4-trimethylquinoline, A/-substituted ureas or thioureas, substituted pyrroles, and nickel or zinc dithiocarbamate salts (see also Antioxidants). The most effective antiozonants, however, are derivatives of -phenylenediamine... 

Table 93 Selected Nickel(II) Complexes with Thiourea, Substituted Thioureas and Related Neutral Monodentate...

This section will be divided into a discussion of reactions carried out starting from thioamides, thioureas, substituted thioureas, dithiocarbamic acids and their ammonium salts, and miscellaneous syntheses. 

In this sequence, substitution by 1 mol of dimethylamine first replaces the benzylmercaptan leading to 5-acetyl-2-dimethylamino-6//-l,3-thiazine (197). The thiazine then undergoes attack by dimethylamine excess at C-6, leading to the thiourea (198). The benzylmercaptan liberated in the first reaction may act as a nucleophile (BzS",H2NMe2+), and a different thiourea substituted by dimethylamino and benzylthio groups is obtained. The action of pyrrolidine on 1,3-thiazine-4-ones (194) can be seen as a Michael addition followed by elimination of H2S. In acidic media, the linear compound obtained is cyclized to the pyrimidone (200) (Scheme 80)... 

Tozawa, T., Misawa, Y., Tokita, S., Kubo, Y., A regioselectively bis (thiourea)-substituted dibenzo-diaza-30-crown-10 a new strategy for the development of multi-site receptors. Tetrahedron Lett. 2000, 41, 5219-5223. 

The use of bifunctional thiourea-substituted cinchona alkaloid derivatives has continued to gamer interest, with the Deng laboratory reporting the use of a 6 -thiourea-substituted cinchona derivative for both the Mannich reactions of malo-nates with imines [136] and the Friedel-Crafts reactions of imines with indoles [137]. In both reports, a catalyst loading of 10-20 mol% provided the desired products in almost uniformly high yields and high enantioselectivities. Thiourea-substituted cinchona derivatives have also been used for the enantioselective aza-Henry reactions of aldimines [138] and the enantioselective Henry reactions of nitromethane with aromatic aldehydes [139]. 

Thirty 5 -thiourea-substituted a-thymidine analogues used to develop receptor-independent 4D-QSARmodels ( 3 = 0.83) for thymidine monophosphate kinase inhibitors. The model was also put into the context of reported crystallographically characterized inhibitor/enzyme interactions... 

Andrade CH, Pasqualoto KF, Ferreira El, Hopfinger AJ (2009) Rational design and 3D-pharmacophore mapping of 5 -thiourea-substituted alpha-thymidine analogues as mycobacterial TMPK inhibitors. J Chem Inf Model 49 1070-1078... 

Khan et al. [9] reported the environment friendly microwave-assisted synthesis of substituted steroidal[6,7-d]thiazoles (iv). The key step involved the reaction of a-haloketones (iii) and thiourea/substituted thiourea via hantzsch protocol. 

A synthesis of thiazolo[5,4-e]indoles from 5-aminoindoles was reported <05TL2865>. The key step was an NBS-mediated regioselective annulation of a 5-thiourea-substituted indole. 

Many compounds have been reported in the literature to be chemical antiozonants, and nearly all contain nitrogen. Compound classes include derivatives of 2,2,4-trimethyl-l, 2-dihydroquinoline, N-substituted ureas or thioureas, substituted pyrroles, and nickel or zinc dithiocarbamate salts. The most effective antiozonants, however, are derivatives of p-phenylenediamine (p-PDA). The commercial materials are grouped into three classes N,N -dialkyl-p-PDAs, Nalkyl-N -ary 1-p-PDAs, and NX-diary 1-p-PI) As. The NX-dialkyl-p-PDAs (where the alkyl group may be 1-methylheptyl, l-ethyl-3-methylpentyl, 1,4-dimethylpentyl, or cyclohexyl) are the most effective in terms of their reactivity to ozone. These derivatives increase the critical stress required for the initiation of crack growth, and they also reduce the rate of crack growth significantly. The sec-alkyl group is most active, for reasons that are not yet completely clear. The drawbacks of these derivatives are ... 

VIII. Compounds containing sulphur (with or without nitrogen and/or halogen). Ammonium salts of simple and substituted sulphonic acids. Sulphonic acids and their metallic salts sxdphonamides. Amino-sulphonic acids. Siilphates of bases. Thiourea, substituted thioureas, thioamides. Sulphonyl halides. iV-Halogeno-sulphonamides. Aldehyde and ketone bisulphite compounds. Thiols. Thio-ethers. Thio-adds. Esters of sulphonic adds. 

Thiourea, substituted thioureas, thioamides Sulphonyl halides N-Halosulphonanudes Aldehyde and ketone bisulphite compounds Thiols TJuo-ethers THo-adds Esters of sulphonic acids... 

A Study by Deng and coworkers demonstrated that the addition of alkanethiols to a.P Unsaturated N-acylated oxazolidin-2-ones is catalyzed by a C6 -thiourea substituted cinchona alkaloid 27, which has a 9-methylanthracyl ether at C9 (Scheme 6.35) [79]. The reaction could be performed with a wide range of alkanethiols and a considerable degree of variations of the unsaturated acceptor. The product of the reaction of 4-methoxybenzyl thiol could subsequently be converted in high yields into a P-thiol ester by removal of the benzylic group and conversion of the oxazolidin-2-one part into an ester. 

New cinchona derivatives are continuously being developed for appUcation in asymmetric organocatalysis. Examples of catalysts obtained by further modification of existing derivatives include an N-oxide of dihydrocupreidine [127], a C6 -N-Boc-glycine-P-isocupreine (53) [128], a C9 thiourea substituted at a remote site with a sulfonamide group (54) [129, 130], and catalysts with an amine as well as a thiourea group (55) [131] (Figure 6.16). 

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