Phenylthioacetic acid

The reported yield3 of 94% could not be achieved. The amount of sulfur can be increased to 12.4 g (0.2 mol) giving a higher yield of phenylthioacetic acid morpholide that contains some unreacted sulfur and a yellow impurity (2-morpholin-4-yl-1-phenyl-2-thioxo-ethanone) that is difficult to remove. 

TLC of the remaining solution (0.25-mm Whatman precoated silica gel plate, 33% ethyl acetate in hexanes) does not show any starting phenylthioacetic acid morpholide. 

Phenylthioacetyl chloride C6H5SCH2COQ. Phenylthioacetic acid is available commerically. 

The sulfur monomeric radical cations (X-S -Y-COOH) were formed from direct ionization of the sulfur atom in parental aromatic carboxylic acids. These X-S -Y-COOH were found to decay by three competitive pathways (i) fragmentation via the cleavage of the C-S bond producing thiyl-type radicals XS, (ii) deprotonation from the methyl/methylene groups adjacent to the sulfur producing a-(alkylthio)alkyl radicals, and (iii) decarboxylation producing C-centered radicals (for phenylthioacetic acid, vide Scheme 6). The efficiency of each pathway is dependent on the structure of the aromatic carboxylic acid studied. 

Monomeric sulfur radical cations derived from various carboxylic acids containing thioether functionality were generated in aqueous solutions using OH radicals. Three decay pathways (decarboxylation, deprotonation, and jS-fragmentation), similar to those presented for phenylthioacetic acid vide supm. Scheme 6), were identified and found to be dependent upon the structure of sulfur radical cations. 

From Figure 23, it is evident that phenylthioacetic acid (point 1) has the highest rate of polymerization and the largest CO2 yields. This is consistent with Eqs. (54) and (55) and the assumption that Or- = Oco2- Based on the analysis above, there is only one radical, a-CBR, capable of initiating polymerization when phenylthio-... 

Phenyl- and 5-aryl-2-benzyl-6//-l,3,4-thiadiazincs 8 (R3 = Ph, Bn) are prepared by condensation of thiobenzohydrazide or phenylthioacetic acid hydrazide with a-halocarbonyl compounds.10, 50 Under appropriate conditions it is also possible to isolate the primarily formed 4,5-dihydro-6//-1,3,4-thiadiazin-5-ol intermediates 7a-h. For this purpose, the thiohydrazide is added to an equimolar amount of sodium ethoxide solution, then at — 25 °C an ethanolic solution of the respective phenacyl bromide, 2-bromo-l,2-diphenylethan-l-one, 2-bromo-l-phenylpropan-l-one, or 2-bromo-l-phenylbutan-l-one is added. The 4,5-dihydro-6//-l,3,4-thiadiazin-5-ols 7 separate as colorless precipitates. They undergo partial dehydration at room temperature to the 2-phenyl- or 2-benzyl-6//-l, 3,4-thiadiazines 8 on heating for about 5-7 minutes in ethanol or chloroform, the dehydration is complete. 

Thiobenzohydrazide (3.04 g, 20 mmol) or phenylthioacetic acid hydrazide (3.32 g, 20 mmol) was treated with NaOEt solution [20 mL from EtOH (20 mL) and Na (0.46 g, 20 mmol)]. The mixture was cooled to - 25 °C with solid C02 and then the a-halo ketone (20 mmol) in anhyd EtOH (20 mL) was added dropwise. A precipitate formed which was separated, and washed with H20. The 4,5-dihydro-6//-1,3,4-thiadiazin-5-ols were purified by dissolution in CHC13 and precipitation with petroleum ether. 

Phenylthioacetic acid, CsHs SCH2COOH. Mol. wt. 168.21, m.p. 64-66. Supplier Aldrich. 

P -Hydroxy sulfides. Phenylthioacetic acid can be converted into the dianion (1) by treatment with 2 eq. of lithium diisopropylamide in THF at 0°. The dianion can be alkylated in high yield. The monoalkylated product can be converted into the fully substituted acid (3) by repetition of the process-conversion to the dianion followed by alkylation. Reduction of (3) with lithium aluminum hydride then gives a 3-hydroxy sulfide (4) in overall yields of 50-90%. 

METHYLENATION N-Methylphenylsulfonimidoylmethyl lithium. Phenylthioacetic acid. Titanium(IV) chloride-Lithium aluminum hydride. Trimethylsilylmethylmag-nesium chloride. 

BUTENOLIDES Phenyl selenenyl chloride. Phenylthioacetic acid. 7-BUTYROLACTONES Ammonium persulfate. Chromic acid, lon-exchangeresins. 

Carboxylic acids of general formula R—X—CHaCOaH (X = O, NH, or S) are known to undergo photosensitized decarboxylation to yield R—X—CHa. The participation of the radicals (167) and (168) in the sensitized photodecarboxylation of phenylthioacetic acid is now supported by the results of a cidnp study.9 ... 

A rather similar CIDNP study (Weinstein et al., 1975) of the photo-oxidation of phenylthioacetic acid by several aryl ketones leads to the conclusion that whilst several radical pairs may give rise to the observed polarization, there is no requirement for the intervention of ion-radical intermediates. It should be noted, however, that, in this case, any primary ion radical intermediates would be extremely short-lived because of facile decarboxylation, e.g. PhSCH2 COOH -> PhSCH2 + COOH. 

BUTENOLIDES Phenyl selenenyl chloride. Phenylthioacetic acid. 

METHYL KETONES Chromic acid. Ethyl a-phenylsulflnylacetate. Lithium acetylide. Lithium diethylamide-Hexamethylphophoric triamide. S-(2-MethoxyallyI)-N,N-dimeth-yldithiocarbamate. a-Methoxyvinyllithium. Phenylthioacetic acid. Potassium tetra-carbonylhydridoferrate. Silver(II) oxide. Trimethylaiuminium. 

---