S- 2- ethyl

Metasystox A trade name for demeton-methyl, C[Pg.257]

An acyclic enone, 2-ethyl-l-phenylprop-2-en-l-one, was reduced with the yeast Pichia stipitis CCT 2617 [19cj. The reduction proceeded chemo- and enantioselec-tively to afford (S)-2-ethyl-l-phenylprop-2-en-l-ol (65% yield, >99% ee). XAD-7 was used to decrease and control the concentration of both the substrate and the product (Figure 8.25). 

In view of the Zr-catalyzed enantioslective carbomagnesation-elimination tandem reaction of allylic derivatives discussed earlier, a similar process with EtjAl might be expected and has indeed been developed recently [29]. As a representative example, the reaction of 2,5-dihydro-furan with 3 equiv. of Et3Al in the presence of (i )-(EBTHI)Zr[B[NOL-(5)] (8) and (NMTHI)ZrCpCl2 (9) produced, after hydrolysis, (S)-2-ethyl-3-buten-1 -ol in 90 and 67% yields, respectively. The enantioselectivity observed with 8 was >99% ee, whereas that observed with 9 was 85-90% ee. Upon deuterolysis of the organoaluminum products, a mixture of monodeuterated and nondeuterated products was obtained and the extent of D incorporation increased to 94% with neat Et3Al without any solvent. The results indicate that the reaction must produce two organoaluminum products, 10 and 11 (Scheme 4.18). On oxidation with 02 only... 

Fig. 7.17 The molecular structures of poly(p -phenylenevinylene), or PPV, (top), poly(2,5-diheptyl-p-phenylenevinylene), or DHPPV (middle) and poly(2-methoxy-S-(2 -ethyl-bexoxy)-p-phenylenevinylene), or MEHPPV (bottom).

In 1952, Rider, Ellinwood, and Coon (7) demonstrated that rats can become tolerant to octamethyl pyrophosphoramide (OMPA). Since then it has been shown that rats can acquire tolerance to a variety of organophosphorus cholinesterase inhibitors. Typical of such reports is that of Bombinski and DuBois (2), who administered 0,0-diethyl S-2-ethyl-2-mercaptoethyl phosphorodithioate (Di-Syston) to rats each day for periods as long as 60 days. Signs of poisoning appeared after 2 days, but began to subside after 7-10 days, even though the activity of brain cholinesterase remained at or about 20% of its normal value from the 5th day onward. 

FIGURE 15.1.4.3.2.1 Logarithm of vapor pressure versus reciprocal temperature for tr/s(2-ethyl hexyl) phosphate. 

Hydrocarboxylation can also be used in the synthesis of heterocycles if the heterofunction is introduced at an appropriate position within the substrate. Thus, preparation of 2,4-disub-stituted 2-buten-4-olides can be achieved via stoichiometric transformation of a protected optically active propargyl alcohol without loss of optical activity30. Sequential treatment with zirconocene chloride hydride (Schwartz s reagent), carbon monoxide, and iodine gives a 55% yield of (S)-2-ethyl-4-isobutyl-2-buten-4-olide30. This reaction resembles the intramolecular hydrocarboxylation of allylic alcohols. 

The optical purity is usually, but not always, equal to enantiomer excess. In order for the two to be equal, it is necessary that there be no aggregation. It is possible, for example, that a homochiral or heterochiral dimer (see Glossary, Section 1.6, for definitions) would refract the circularly polarized light differently than the monomer (or each other). In 1968 [19] Krow and Hill showed that the specific rotation of (S)-2-ethyl-2-methylsuccinic acid (85% ee) varies markedly with concentration, and even changes from levorotatory to dextrorotatory upon dilution. In 1969 [20], Horeau followed up on Krow and Hill s observation, and showed that the optical purity (at constant concentration) and enantiomer excess of (5)-2-ethyl-2-methylsuccinic acid were unequal except when enantiomerically pure or completely racemic. This deviation from linearity is known as the Horeau effect, and its possible occurence should be remembered when determining enantiomeric purity by polarimetry. 

Demeton. Phosphorothioie acid O.O-dtethyl 0-/2-tethylthioiethyl] ester mixture with 0,0-dielhyl S-[2-(ethyl-thio)ethyljpkosphorothioate mercaptophos Bayer 8169 E-1059 Systox. C-H OjPSj mol wt 258.34. C 37.19%, H 7.41%, O 18.58%, P 11.99%, S 24.82%, Isomeric mixture consisting of demeton -O and demeton -S (O.O-diethyl OCand S)-ethylmercaptoethyl thiophosphates). Another name for demeton -S is Isosystox. Prepn Schrader, U,S. pats. 2,571, 989 and 2.597,534 (1951, 1952 both to Bayer) Gardner. Heath, Anal. Chem. 25, 1849 (1953). 

Di methy l-S-2-(ethyl sulfi ny I) ethyl phosphorothioate. See Oxydemeton-methyl 0,0-Dimethyl-S,2-(ethylthio) ethyl phosphorothioate. See Demeton-S-methyl Demetonmethyl... 

Miscellaneous Aqueous and fatty extractants Bis-2-ethyl hexyl) adipate, f /s(2-ethyl-hexyl phthalate), octadecyl 3- (3,5 di-tert butyl- 4- hydroxy phenyl) propionate (Irganox 1076) Gas chromatography [170]... 

C22H42O2S2 hexanedithioic acid bis-S-(2-ethyl-hexyl) ester 102885-13-2... 

Five-carbon compounds are formed from (S)-aceto-2-hydroxy-butyric acid, also known as (S)-2-ethyl-2-hydroxy-3-oxobutanoic acid, which is the intermediate of isoleucine biosynthesis from threonine. This acid is formed in the reaction of 2-oxobutanoic acid with acetaldehyde and its decarboxylation provides R)-3-hydroxypentane-2-one, which is oxidised to pentane-2,3-dione and reduced to (21 ,31 )-pentane-2,3-diol (Figure 8.13). 

Chem., Int. Ed., 13, 608—609 (b) Rambeck, B. and Simon, H. (1974) Stereospecific hydrogenation of (R)- or (S)-2-ethyl-4-phenylallenecarboxylic acid to cis- or trans-2-ethyl-4-phenyl-3-butenecarboxylic add by means of Clostridium Iduyveri. Angew. Chem., Int. Ed., 13, 609. 

Disulfoton (0,0-diethyl S-[2-(ethyl-thio)ethyl] phosphorodithio-ate) - 261... 

---