Activator s

Furthermore, the catalytic allylation of malonate with optically active (S)-( )-3-acetoxy-l-phenyl-1-butene (4) yields the (S)-( )-malonates 7 and 8 in a ratio of 92 8. Thus overall retention is observed in the catalytic reaction[23]. The intermediate complex 6 is formed by inversion. Then in the catalytic reaction of (5 )-(Z)-3-acetoxy-l-phenyl-l-butene (9) with malonate, the oxidative addition generates the complex 10, which has the sterically disfavored anti form. Then the n-a ir rearrangement (rotation) of the complex 10 moves the Pd from front to the rear side to give the favored syn complex 6, which has the same configuration as that from the (5 )-( )-acetate 4. Finally the (S)-( )-mal-onates 7 and 8 are obtained in a ratio of 90 10. Thus the reaction of (Z)-acetate 9 proceeds by inversion, n-a-ir rearrangement and inversion of configuration accompanied by Z to isomerization[24]. 

Hydrolysis of (R) (—) 2 bromooctane by the 8 2 mechanism yields optically active (S) (-f) 2 octanol The 2 octanol obtained by hydrolysis of racemic 2 bromooctane is not optically active... 

W. W. Eckenfelder, Jr. and J. L. M xsX.e-un2vn, Activated S ludge Treatment of Industrial Wastewater, Technomic Publishing Company, Lancaster, Pa.,... 

G. M. Shaul, C. R. Dempsey, and K. A. Dostol, Fate of Water Soluble A p Djes in the Activated S ludge Process, EPA/600/2-88/030, report of the Water Engineering Research Laboratory, Office of Research and Development, USEPA, Cincinnati, Ohio, July, 1988. 

Table 1 Hormonal cross-reactivity of three Type of activity s ...

In this terminoiogy, pozzoiana cement is C mixed with a voicanic ash which has active S on its surface. The reactions which occur when it sets (Fig. 20.1) are... 

Activity R = Raman-active, ir = infrared-active, S = optically silent, observed in neutron scattering. tCarbon atom displacement il or J. to C. 

Fpobtem Suggest a synthesis of optically active S-(+)-sulcatol (13), the aggregation pheromone of the wood-boring ambrosia beetle, from available ethyl (S)-(-)-lactate (14). 

In the reduction of racemic y -ketosulphoxides (e.g. 464a) with actively fermenting yeast (Saccharomyces cerevisiae) the enantiomers are reduced at sufficiently different rates to allow isolation of optically active -hydroxy sulphoxide 524 and unreacted optically active )S-ketosulphoxide with at least 95% optical purity (equation 323). 

Carbanions derived from optically active sulfoxides react with esters, affording generally optically active )S-ketoesters ° . Kunieda and coworkers revealed that treatment of (-t-)-(R)-methyl p-tolyl sulfoxide 107 with n-butyllithium or dimethy-lamine afforded the corresponding carbanion, which upon further reaction with ethyl benzoate gave (-l-)-(R)-a-(p-tolylsulfinyl)acetophenone 108. They also found that the reaction between chiral esters of carboxylic acids (R COOR ) and a-lithio aryl methyl sulfoxides gave optically active 3-ketosulfoxides The stereoselectivity was found to be markedly influenced by the size of the R group of the esters and the optical purity reached to 70.3% when R was a t-butyl group. 

By modification of the elegant method of preparation of optically active sulfinates previously reported by Mikolajczyk and coworkers , an efficient stereospecific method for the conversion of readily available optically active sulfinamides to optically active sulfinates of inverted configuration at the sulfinyl function, has been recently reported by Hiroi and coworkers . The same authors subsequently reported the thermal rearrangement of several optically active cis- and trans-y-substituted allylic p-toluenesulfinates to optically active chiral sulfones with high stereoselectivity. For example, trans and cis (S)-( — )-crotyl p-toluenesulfinates rearranged to optically active (S)-(-l-)- and (R)-( — )-a-methylallyl p-tolyl sulfone, respectively (equation 19). 

The letters on Figure 13-1 refer to the activities given in Table 13-1, and the number in parentheses that follows each letter is the time necessary to complete the activity. Activities S and T are dummy activities that take no time to complete. For CPM and PERT diagrams, it is a rule that no two arrows can be connected to the same two nodes. Note that if it were not for the dummy activities, the arrows... 

Ring-opening polymerization of racemic a-methyl-/J-propiolactone using lipase PC catalyst proceeded enantioselectively to produce an optically active (S)-enriched polymer [68]. The highest ee value of the polymer was 0.50. NMR analysis of the product showed that the stereoselectivity during the propagation resulted from the catalyst enantiomorphic-site control. 

The photoelimination of nitrogen from 1-pyrazolines is one of the most thoroughly investigated photoreactions and it has been used extensively in the synthesis of cyclopropane derivatives.334 Both stereospecific and non-stereospedfic processes have been observed and these are believed, at least in simple 1-pyrazolines, to correspond to singlet and triplet excited states, respectively. Two reaction pathways have been proposed in the azoalkane 405335 direct excitation via a thermally activated S, state affords the C6H6 isomers 406 to 409, whereas triplet-sensitized excitation results in a tem-... 

Oshikawa, T. and Yamashita, M., Preparation of optically active (S)-2-ami-noalkylphosphonic acids from (S)-amino acids without racemization, Bull. Chem. Soc. Jpn., 63, 2728, 1990. 

The unified highly convergent total and formal syntheses of ( + )-macro-sphelides B (441 X = O) and A (441 X = a-OH, p-H), respectively, have been described (483). Key features of the syntheses include the concise synthesis of the optically active S-hydroxy-y-keto a, 3-unsaturated acid fragment 442 via the direct addition of a fra/i.s-vinylogous ester anion equivalent to a readily available Weinreb amide, and the facile construction of the 16-membered macrolide core of the macrosphelide series via an INOC. 

Most optically active polysilanes owe their optical activity to induced main-chain chirality, as outlined above. However, backbone silicon atoms with two different side-chain substituents are chiral. Long-chain catenates, however, are effectively internally racemized by the random stereochemistry at silicon, and inherent main-chain chirality is not observed. For oligosilanes, however, inherent main-chain chirality has been demonstrated. A series of 2,3-disubstituted tetrasilanes, H3Si[Si(H)X]2SiH3 (where X = Ph, Cl, or Br), were obtained from octaphenylcyclote-trasilane and contain two chiral main-chain silicon atoms, 6.16 These give rise to four diastereoisomers the optically active S,S and R,R forms, the activity of which is equal but opposite, resulting in a racemic (and consequently optically inactive) mixture and the two meso-forms, S,R and R,S, which are optically inactive by internal compensation. It is reported that the diastereoisomers could be distinguished in NMR and GC/MS experiments. For the case of 2-phenyltetrasilane, a racemic mixture of (R)- and (A)-enantiomers was obtained. 

---