S-alkylations

6-Mercaptobenzimidazo[l,2-c]quinazoline reacts with dibromo derivatives under PTC conditions (K2C03/TBAB). Microwave irradiation enabled a striking reduction in reaction times (12 h compared with 15 min) with similar yields (86 and 81%) when compared with conventional heating (Eq. 40) [61]. 

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S-Alkyl-iso-thiuronium picrates. Alkyl bromides or iodides react with thiourea in alcoholic solution to produce S-alkyl-iso-thiuronium salts, which yield picrates of sharp melting point ... 

Place a mixture of 0-5 g. of finely powdered thiourea, 0-5 g. of the alkyl halide and 5 ml. of alcohol in a test-tube or small flask equipped with a reflux condenser. Reflux the mixture for a j)eriod depending upon the nature of the halide primary alkyl bromides and iodides, 10-20 minutes (according to the molecular weight) secondary alkyl bromides or iodides, 2-3 hours alkyl chlorides, 3-5 hours polymethy lene dibromides or di-iodides, 20-50 minutes. Then add 0 5 g. of picric acid, boil until a clear solution is obtained, and cool. If no precipitate is obtained, add a few drops of water. RecrystaUise the resulting S-alkyl-iso-thiuronium picrate from alcohol. 

HaUde B.P. M.P.. 20 20 D 1 i. 4nUlde i i a-Naphtha- llde Alkyl 1 Mercuric i Halide S-Alkyl-ito- thiuronlum Picrate Picrate of Q-naphthyl ether... 

Ethyl /m s -2-butenyl sulfone (86) together with some ethyl vinyl sulfone are obtained by the reaction of ethylene and. SO2 in wet benzene using PdCl2. SO2 behaves mechanistically similarly to CO in this reaction[66]. Hydrosulfination of alkenes with SO2 and H2 is catalyzed by the Pd(dppp) complex. The sulfinic acid 87 is a primary product, which reacts further to give the. S-alkyl alkanethiosulfonates 88 as the major product, and 89 and the sulfonic acid 90 as minor products[67]. 

In 1890, Gabriel and Lauer (92) established that a-bromoamines react with CS2 to give 2-mercaptothiazolines (61). In the same laboratory, Hirsch (93) reacted /x-mercapto -methylthiazoline (61) with various alkyl iodides and obtained the corresponding S-alkyl derivatives. 

One example of nucleophilic attack by a rr-electron system on a sulfur atom of a thiirane 1-oxide is shown in Scheme 51. S-Alkylthiirenium ions react with tetramethylethylene to transfer the S-alkyl group yielding the alkyne and an S-alkyl-2,2,3,3-tetramethylthiiranium ion (79MI50600). 

Benzimidazoline, 2,2-bis(trifluoromethyl)-synthesis, 5, 471 Benzimidazolines acidity, 5, 425 Benzimidazolinethiones Mannich reaction, 5, 390 synthesis, 5, 460 Benzimidazoline-2-thiones alkylation, 5, 444—445 S-alkylation, 5, 444 mercuration, 5, 445 reactions... 

Pyrimidine-2-sulfonyl chloride, 4,6-dimethyl-reactions, 3, 97 Pyrimidinesulfonyl halides reactions, 3, 97 Pyrimidinethiols S-acylation, 3, 95 S-alkylation, 3, 94 oxidation, 3, 94 synthesis, 3, 135 Pyrimidine-5-thiols oxidation, 3, 94 synthesis, 3, 136... 

Pyrimidine-2-thione, 4,5-diamino-S-alkylation, 3, 94 Pyrimidine-2-thione, dihydrosynthesis, 3, 109... 

O-Trimethylsilyl-S-alkyl, 344 O-Alkyl-S-alkyl or -S-phenyl, 345 0-Methyl-S-2-(methylthio)ethyl, 346... 

In addition to its uses in photography and medicine, iodine and its compounds have been much exploited in volumetric analysis (iodometry and iodimetry, p. 864). Organoiodine compounds have also played a notable part in the development of synthetic organic chemistry, being the first compounds used in A. W. von Hofmann s alkylation of amines (1850), A. W. Williamson s synthesis of ethers (1851), A. Wurtz s coupling reactions (1855) and V. Grignard s reagents (1900). 

Ethyl iodide and 5-amino-2-methyl-l,3,4-thiadiazole react at 110° to give the N-3 salt (78 R = Me, R = NH2, R" = Et), as shown by the presence of the very reactive methyl group this salt is also used to prepare cyanine dyes. The slow quatemization at the ring-nitrogen atom furthest from the amino group is consistent with the reactions observed in other ring systems. As would be e pected, 5-alkylthio-2-methyl-l,3,4-thiadiazoles form salts at the N-3 (78 R = Me, R - S-alkyl).i ... 

Tlie oxo-thione form 241 is taken for 2-mercapto-4-hydroxyimidazoles (Scheme 83) [76AHC(S1), p. 463]. These tautomeric equilibria were clarified by the consideration of models in which some tautomeric forms were blocked. Thus, for S-alkylated 5,5-diphenyl 242 or 5-spirocyclohexyl 243 derivatives, oxo-thiol forms are the major tautomers [73T3565 76AHC(S1), p. 463]. 

Mercapto-3-methyl-4//-pyrido[],2-rz]pyrimidin-4-one and its 6,7,8,9-tetrahydro derivative were S-alkylated with 4-substituted benzylbromides (96EUP733633). 

When an S-alkyl-A A -disubstituted isothiourea reacts with diketene in a boiling solvent, 2-imino-4-keto-3,4-dihydro-l,3-2i/-oxazine derivatives (45) are formed. Analogous compounds can be prepared from dialkylcarbodiimides and diketene. ... 

By Production of Thiepinium Salts by S-Alkylation of Thiepin Derivatives... 

S-Alkylation of 9-methoxy-5//-pyrido[3.2-e]azcpine-7(6//)-thione (10), prepared from the pyridoazepin-7-one 9 with phosphorus pentasulfide in pyridine, is achieved to give 11 in high yield with iodomethane in basic solution.191... 

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