S 4-methoxy

The (2R,3R,4R) diastereomer results from partial racemization of one or both of the allenylmetal intermediates. This point was confirmed by comparison to authentic material as the (S)-MPA ((S)-(2-methoxy)phenylacetic acid-Mosher s acid) derivative. The optical rotations of these compounds are small, and thus correlation by comparison of [ajp... 

S)-2-Methoxy-3,4-dihydro-2tf-pyran (1.14 g, 10 mmol) was added to a solution of i-Bu3Al (21 mmol) in hexane (20 mL) at 68 °C and heated at this temperature for 18 h. The mixture was cooled to 0 rC. and hydrolyzed with H20. The organic product was extracted with Et20 (4x 50 mL) and the ethereal extracts were washed with H20, dried (K2C03) and the solvent was removed. Distillation of the crude product gave the pure compound yield 85% bp 91 -93 °C/20 Torr [a], 5 16.12 (10 cm, neat) (38% ee, Mosher ester). 

Groves et al. found that a simple heme-iodosobenzene system mimics the enzymic reactions.127 Cyclohexane and cyclohexene are oxidized to cyclohexanol and a mixture of cyclohexene oxide and cyclohexenol respectively by this system. Using meso-tetrakis-a,/J,a,/J-(o-acylamidophenyl)por-phinatoiron(III) chloride where the acyl group is (i )-2-phenylpropionyl or (S)-2 -methoxy-carbonyl-l,T-binaphthyl-2-carbonyl, optically active styrene oxides are obtained in 51% e.e. The Fe(TPP)Cl-PhIO system can also oxygenate arenes to arene oxides.128 Based on the following observations, mechanisms involving O—Felv(Por) t as the active species have been proposed (Scheme 30).127... 

Benzol-dithiophosphonsaure-S-(2-methoxy-5-oxo-4,5-dihydro-1, 3,4-thiadiazol-4-ylmethylester)-0-methylester 60% Schmp. 84-86°... 

Benzol- -S-(ethoxycarbonyl-methylester)-0-cthyl-ester Xll/1, 589 Benzol- -O-ethylester E2, 453 Kalium-Salz XII/1, 583 Benzol- -S-ethylester XII/1, 585 Benzol- -O-ethylester-S-Anhydrid E2, 438 Benzol- -0-ethylester-S-(2-methoxy-5-oxo-4,5-dihydro- 1,3,4-thiadiazol-4-ylmethylester) E2, 455 Benzol- -O-ethylester-S-morpholinoester E2, 458 aus Benzol-thiophosphonigsaure-O-ethylester und Morpholin-4-sulfensaurechlorid E2, 459 Benzol- -S-(2-ethylthio-ethylester)-0-isopropyl-ester XII/1, 588... 

The Step 2 product mixture was resolved using MA -dicyclohcxylcarbodiimide and ( S )-2-methoxy-2-phenylacetic acid. 

Thiophosphorsaure -S-(2-methoxy-carbonyl-ethylester) (Dinatrium-Salz) XII/2, 589... 

Butadiene 3-[(S)-2-(Methoxy-methyl)-pyrrolidin-3-methyl-E21c, 2796 (R2NH + Butan-dion)... 

On the other hand, Hisaeda and coworkers [504] found that the vitamin Bi2-mediated electroreductive optical resolution was accompanied by rearrangement Electroreduction of racemic 3-bromo-2-methoxy-2-phenylpropionate using a hydrophobic vitamin Bi2 mediator afforded ethyl (S)-2-methoxy-2-phenylpropionate in 55% ee, while a novel hydrophobic vitamin Bj2 modified by introducing a 1,3-phenylene diacetyl moiety into the peripheral site around the corrin s B ring, a so-called strapped hydrophobic vitamin B12, provided the corresponding R-enantiomer in 26% ee. 

Substituted aliphatic and aromatic a-keto ethers (see Figure 2.7) are also amenable to enantioselective hydrogenation catalyzed by cinchona-modified Pt catalysts [34], However, as opposed to the achiral ketones discussed above, kinetic resolution is observed for these chiral substrates. At conversions of 20-42%, ee values of 91-98% were obtained when starting with a racemic substrate. While the very high initial ee values were impressive, it was also dear that this method with yields of less than 50% and gradually decreasing ee values is of little preparative value. The obvious solution was to attempt dynamic kinetic resolution in the presence of a base. Indeed, with OH -activated Amberlites dynamic kinetic resolution was observed. Both (R,S)-2-methoxy cyclohexanol and (R,S)-2-methoxy-l,2-diphenyl ethanol can be obtained... 

Dimethyl-S-(l,2,3-benzotriazinyl-4-keto)methyl Phosphorodithloate 0,0-Dimethyl S-(3,4-Dihydro-4-keto-l,2,3-benzotriazinyl-3-methyl) Dithiophosphate 0,0 -Dimethyl-S-[(2-methoxy-l,3,4-thiadiazol-5(4H)-one-4-yl)methyl] Dithiophosphate 0,0-Dimethyl S-4-Oxo-l,2,3-benzotriazin-3(4H)-ylmethyl Phosphorodlthioate 0,0-Dimethyl-S-(4-oxobenzotriazin-3-methyl)-dithiophosphat... 

Yamamoto et al. ° have examined the addition of allyl organometallic reagents to a-alkoxyaldimines (40) derived from (S)-2-methoxy(methoxy)propionaldehyde and (/ )- and (S)-l-phenylethylamine (equation 10). The results are summarized in Table 10. Chelation control with allyl-AlEtaMgCl, -MgCTl and -ZnBr (entries 1-3, Table 10) and nonchelation (Cram) control with allyl-Ti(Pi O)3, -B(OMe)2 and -9-BBN (entries 4-6, Table 10) parallels that observed in the allyl metal-a-alkoxyaldimine additions (involving aldimines that lack a chiral nitrogen substituent) shown in Table 6. The chirality of the a-alkoxy... 

Entry Allyl organometallic Product ratio (S)-2-( Methoxy)methoxypropanal additions... 

Dimethoxyphosphinothioylthiomethyl-5-methoxy-1,3,4-thiadlazol-2(3H)-one OMTP (insectic-ide) ENT 27193 EPA Pesticide Chemical Code 100301 Fisons NC 2964 Geigy 13005 Geigy GS-13005 GS 13005 HSDB 1594 Methidathion Metidation QMS 844 (0,0-Dimethyl)-S-(-2-methoxy-delta(sup2)-1.3,4-thiadiazolin-5-on-4-ylmethyl)dithio-phosphate 0.0-Di-methyl-S-(2-methoxy-1,3,4-thiadiazol-5(4H)-onyl-(4)-methyl) dithiophosphat 0,0-Dimethyl-S-(2-methoxy-1,34-thiadiazol-5(4H)-onyl-(4)-methyl)-phosphorodithi-oate 0,0-Dimethyl-S-((2-methoxy-1,3,4(4H)thiodiazol-5-on-4-yl)-methyl)-dithiofosfaat 0,0-Dimethyl S-(2,3-dihydro-5-nnethoxy-2-oxo-... 

---