Acetyl thiourea

MERCAPTANS 1 -Acetyl-2-thiourea. METHANESULFONATE ESTERS Meth-anesulfonyl chloride. 

Acetyl cyclohexane sulfonyl peroxide, 7 Acetyl Iodide, 7 Acetyl thiourea, 8 Acetylaminofluorene, 7 Acetylene, 7... 

N, N-Diphenylthiourea, (CcH.s N.CS.N, flat prisms (from ale), mp 212—13° with frothing to a gm liq. It can be prepd by heating N,N-diphenyl N -acetyl-thiourea with alcoholic NaOH, (Ref 2)... 

A solution of 69 g of sodium in 1,380 cc of absolute alcohol is mixed with 257.4 g of p-methylthioethyl-(l-methyl)-n-butyl-cyano-acetic acid ethyl ester and 114 g of thiourea and the whole mass boiled under reflux with stirring for six hours. After concentration under vacuum the residue is taken up in 1.5 liters of water and shaken up thrice, each time with 300 cc of ether. The aqueous alcoholic layer is stripped, under vacuum, of the dissolved ether and mixed with 300 cc of 30% acetic acid under stirring and ice cooling. The precipitated material is sucked off, washed with water, dried and recrystallized from isopropyl alcohol. The thus obtained p-methyl-thioethyl-(l-methyl)-n-butyl-cyano-acetyl thiourea forms yellowish green crystals having a melting point of 229°C to 230C. 

Acetoiicetyliition Reactions. The best known and commercially most important reaction of diketene is the aceto acetylation of nucleophiles to give derivatives of acetoacetic acid (Fig. 2) (1,5,6). A wide variety of substances with acidic hydrogens can be acetoacetylated. This includes alcohols, amines, phenols, thiols, carboxyHc acids, amides, ureas, thioureas, urethanes, and sulfonamides. Where more than one functional group is present, ring closure often follows aceto acetylation, giving access to a variety of heterocycHc compounds. These reactions often require catalysts in the form of tertiary amines, acids, and mercury salts. Acetoacetate esters and acetoacetamides are the most important industrial intermediates prepared from diketene. 

Furium. N[4-(5-Nitro-2-furanyl)-2-thia2olyl]acetamide, has demonstrated activity against baciUi and pathogenic enterobacteria (24). The product, prepared from thiourea and 2-bromo-l-(5-nitro-2-furanyl)ethanone followed by acetylation of the intermediate aminothia2ole with acetic anhydride in pyridine (25), is marketed in several countries for both human and veterinary use. 

As demonstrated above, nitro derivatives of five-membered heterocycles have found extensive use as antiinfective agents. It is therefore of interest that the nitro derivative of a substituted thiazole was at one time used as an antitrichomonal agent. Bro-mination of 2-aminothiazole (136) (obtained from condensation of thiourea with chloroacetaldehyde) gives the 4-bromo derivative (138) this is then acetylated to 139. Treatment of 139 with nitric acid leads to an interesting displacement of bromine by a nitro group to afford aminitrazole (140)... 

An acylated glycosyl halide, such as a 2,3,4,6-tetra-O-acetyl derivative, is treated with thiourea. The resulting pseudothiouronium salt is hydrolyzed with aqueous potassium carbonate to give the 2,3,4,6-tetra-0-acetyl-l-thio-(3-D-glucopyranose,48 which then is alkylated. 

From the diverse examples on Hantzsch syntheses reported, the reaction of 2-bromo-4 -methylacetophenone and l-acetyl-2-thiourea was exemplarily chosen to be represented here [10]. 

Remove unreacted N-acetyl homocysteine thiolactone and reaction by-products by gel filtration or dialysis against lOmM sodium phosphate, 0.15M NaCl, lOmM EDTA, pH 7.2. Other buffers suitable for individual protein stability may be used as desired. For the silver nitrate-containing reaction, removal of the silver-thiourea complex may be done by adsorption onto Dowex 50, and the protein subsequently eluted from the resin by 1M thiourea. Removal of the thiourea then may be done by gel filtration or dialysis. 

Type D synthesis, where the 3,4-CN bond is being formed, involves the reaction of thiosemicarbazones of aldehydes, ketones, and esters 97 with 3,3-pentamethyleneoxaziridine 98 to afford 5-imino-3,3-pentamethylene-l,2,4-thiadi-azolidines 99 (Equation 27). yV-Acylthioureas also undergo this transformation but, whereas this reaction is fairly general for thiosemicarbazones, only acetyl and benzoyl thioureas give 1,2,4-thiadiazolidines <1996CHEC-II(4)307>. There have been no new reports of type D syntheses since the publication of CHEC-II(1996). 

The acyl-Pictet-Spengler reaction is also catalyzed by chiral thiourea derivative 6 to provide M-acetyl p-carbolines in high enantioselectivities. Notably, thiourea derivatives can activate not only electronically distinct imine derivatives such as N-alkyl and N-Boc imines but also a weakly Lewis basic N-acyhminium ion with high enantioselectivity using a chiral hydrogen bond donor (Scheme 12.4). 

In 2004, Taylor and Jacobsen suggested a procedure for the enantioselective acetyl-Pictet-Spengler reaction, that is the cyclization of electron-rich aryl or heteroaryl groups onto N-acyliminium ion enabling access to substituted tetrahydro-P-carbolines and tetrahydroisoquinolines that are core structure elements in natural and synthetic organic compounds [202, 203]. Screening various thiourea catalyst candidates such as 47 in the formation of model product Np-acetyl-... 

Figure 6.17 Pyrrole thiourea derivatives evaluated for catalytic activity and selectivity in the asymmetric acetyl-Pictet-Spengler reaction.

Scheme 6.82 Proposed reactive complex of the Petasis reaction utilizing a-hydroxy aldehydes, amines, and organic boronic acids (A) and bifunctional mode of action of chelating thiourea catalyst 65 in the enantioselective Petasis-type 2-vinylation of N-acetylated quinolinium ions (B).

Figure 6.21 Chelating thiourea derivatives screened in the Petasis-type 2-vinylation of the N-acetylated quinolinium ion at -65 °C.

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