1 - propane, asymmetric

S)-2-(6-Methoxy-2-naphthyl)propanal [Asymmetric Hydroformylation of a Vinylarene under Homogeneous Conditions]/" A deoxygenated so... 

Although the blast effects of the East St. Louis tank-car accident (NTSB 1973) were found to be highly asymmetric, average TNT equivalencies of 10% on an energy basis and 109% on a mass basis were found. These equivalencies were calculated based on the assumption of a full tank-car inventory (55,000 kg) of a mixture of propylene and propane. 

Scheme 6a presents the synthesis of fragment 15. Intermediate 15 harbors two vicinal stereogenic centers, and is assembled in a very straightforward manner through the use of asymmetric aldol methodology. Treatment of the boron enolate derived from 21 with 3-[(p-methoxybenzyl)oxy]propanal (22) affords crystalline syn aldol adduct 34 in 87 % yield as a single diastereomer. Transamination to the A-methoxy-A-methylamide,20 followed by silylation of the secondary hydroxyl group at C-19 with triethylsilyl chloride, provides intermediate 15 in 91 % yield. 

Z)-l-Methyl-2-butenylboronate 7 undergoes an exceptionally enantioselective reaction with benzaldehyde (99% ee), propanal (79%. 98% ee), 2-methyl-2-propenal (85%, 99% ee), and ( )-2-methyl-2-pentenal (81 %, 99% ee)10 38. Excellent enantioselectivity is also realized in reactions of the analogous chiral a-methyl-) y-disubstituted allylboronate27 40. Whether the l,2-dicyclohexyl-l,2-ethanediol auxiliary plays a beneficial role in this reaction, as suggested above for the asymmetric allylboration reactions of 6, has not yet been determined. 

The matched double asymmetric reactions with (7 )-l and (a.R,S,S)-2 provide the (S,Z)-diastereomer with 94% and 96% selectivity, while in the mismatched reactions [(S)-l and (aS,R,R)-2] the (S.Z)-diastereomer is obtained with 77% and 92% selectivity, respectively. Interestingly, the selectivity of the reactions of (/ )-2,3-[isopropylidenebis(oxy)]propanal and 2 is comparable to that obtained in reactions of (7 )-2,3-[isopropylidenebis(oxy)]propanal and the much more easily prepared tartrate ester modified allylboronates (see Table 7 in Section 1.3.3.3.3.1.5.)41. However, 2 significantly outperforms the tartrate ester allylboronates in reactions with (5)-2-benzyloxypropanal (Section 1.3.3.3.3.1.5.), but not the chiral reagents developed by Brown and Corey42-43. 

However, with aldehydes from which a very high substrate-based asymmetric induction originates12, such as 2-(tetrahydro-2f/-pyranyloxy)propanal or cw-(2J ,3fJ)-2,3-0-isopropylidene-... 

The addition of the lithium azaenolate of the SAMP hydrazone of propanal to methyl (E)-2-butenoate to furnish the (S,S,S)-adduct in 58% yield with > 96% ee and de is illustrative for the efficiency of this asymmetric Michael addition10°. Only the anti-isomer (an / adduct) is found. This methodology was used in the synthesis of pheromones of the small forest and red wood ant200. 

Propane, (J )-1,2-bis(diphenylphosphino)-rhodium complexes asymmetric hydrogenation, 6, 251... 

Numerous examples have been pubhshed dealing with the heterogeneization of copper complexes, as immobihzed catalysts for the asymmetric cyclo-propanation of alkenes. Some of them have already been mentioned in the text for a direct comparison with their homogeneous coimterparts. Other reusable catalytic systems have been developed and will be described as follows. 

The above-described structures are the main representatives of the family of nitrogen ligands, which cover a wide spectrum of activity and efficiency for catalytic C - C bond formations. To a lesser extent, amines or imines, associated with copper salts, and metalloporphyrins led to good catalysts for cyclo-propanation. Interestingly, sulfinylimine ligands, with the chirality provided solely by the sulfoxide moieties, have been also used as copper-chelates for the asymmetric Diels-Alder reaction. Amide derivatives (or pyridylamides) also proved their efficiency for the Tsuji-Trost reaction. 

As another successful application of Noyori s TsDPEN ligand, Yan et al. reported the synthesis of antidepressant duloxetine, in 2008. Thus, the key step of this synthesis was the asymmetric transfer hydrogenation of 3-(dime-thylamino)-l-(thiophen-2-yl)propan-l-one performed in the presence of (5,5)-TsDPEN Ru(II) complex and a HCO2H TEA mixture as the hydrogen donor. The reaction afforded the corresponding chiral alcohol in both high yield and enantioselectivity, which was further converted in two steps into expected (5)-duloxetine, as shown in Scheme 9.17. 

Dimethylsulfoxide -1.3 OS-phosphate buffer pH 7.1 (1/3) Pseudomonas cepecia lipase Asymmetrical hydrolysis of( + )1 -chloro-2-acetoxy-3-(l-naphthyloxy)-propane 82.3 8... 

Introduction Since we had already developed the novel asymmetric addition of lithium acetylide to ketimine 5, we did not spend any time on investigating any chiral resolution methods for Efavirenz . Our previous method was applied to 41. In the presence of the lithium alkoxide of cinchona alkaloids, the reaction proceeded to afford the desired alcohol 45, as expected, but the enantiomeric excess of 45 was only in the range 50-60%. After screening various readily accessible chiral amino alcohols, it was found that a derivative of ephedrine, (1J ,2S) l-phenyl-2-(l-pyrrolidinyl)propan-l-ol (46), provided the best enantiomeric excess of 45 (as high as 98%) with an excellent yield (vide infra). Prior to the development of asymmetric addition in detail, we had to prepare two additional reagents, the chiral modifier 46 and cyclopropylacetylene (37). 

Catalysts of the Co(salen) family incorporating chiral centers on the ligand backbone are useful in asymmetric synthesis and the field has been reviewed.1377,1378 In two examples, the hydroxy-lation reaction (Equation (14)) involving (269) proceeds with 38% ee,1379 whereas the cyclo-propanation reaction with (271) (Equation (15)) proceeds with 75% ee and with 95 5 trans cis.1380 A Co(V) salen carbenoid intermediate has been suggested in these reactions. 

In 1966, Nozaki et al. reported that the decomposition of o-diazo-esters by a copper chiral Schiff base complex in the presence of olefins gave optically active cyclopropanes (Scheme 58).220 221 Following this seminal discovery, Aratani et al. commenced an extensive study of the chiral salicylaldimine ligand and developed highly enantioselective and industrially useful cyclopropanation.222-224 Since then, various complexes have been prepared and applied to asymmetric cyclo-propanation. In this section, however, only selected examples of cyclopropanations using diazo compounds are discussed. For a more detailed discussion of asymmetric cyclopropanation and related reactions, see reviews and books.17-21,225... 

While investigating the reaction of ZnPf2 with pyrimidine-5-carboxaldehyde 190, the Soai group made the important discovery that these two compounds reacted in the presence of a catalytic amount of (enantiomeric purity (as low as 2%) to furnish the same alcohol as the addition product with ee s up to 89% (Scheme 106). This most remarkable finding was the first case of asymmetric amplification in autocatalytic reactions.275... 

For more examples of chiral bis(sulfonamide) catalyzed asymmetric cyclo-propanation, see Denmark, S. E. O Connor, S. P. Wilson, S. R. Angew. Chem. Int. Ed. Engl. 1998, 37, 1149, and the references cited therein. 

The asymmetric hydroformylation of functionalized aliphatic alkenes is generally more difficult than the hydroformylation of vinyl arenes. The rhodium-catalyzed hydroformylation of vinyl acetate (36) yields 2- and 3-acetoxypropanals, 37 and 38, with high chemoselectivity. Ethyl acetate and acetic acid can also be found as by-products. One of the potential applications of vinyl acetate hydroformylation is the production of enantiopure propane 1,2-diol (Scheme 6). 

The first asymmetric procedure consists of the addition of R2Zn to a mixture of aldehyde and enone in the presence of the chiral copper catalyst (Scheme 7.14) [38, 52]. For instance, the tandem addition of Me2Zn and propanal to 2-cyclohexenone in the presence of 1.2 mol% chiral catalyst (S, R, R)-1S gave, after oxidation of the alcohol 51, the diketone 52 in 81% yield and with an ee of 97%. The formation of erythro and threo isomers is due to poor stereocontrol in the aldol step. A variety of trans-2,3-disubstituted cyclohexanones are obtained in this regioselective and enantioselective three-component organozinc reagent coupling. 

Sulfoxide (N)-(+)-(151) undergoes a highly diastereoselective asymmetric cyclo-propanation with diphenyldiazomethane and diphenylsulfonium isopropylide to form the corresponding cyclopropanes (152) (Scheme 18). A mechanistic rationale to account for the observed stereoselectivities is illustrated for Ph,CN2 (153). ... 

As you can see very clearly, propan-2-ol does not contain an asymmetric carbon, as all the four groups attached to the tetrahedral carbon are not different. Thus It Is an achiral molecule. 

For the preparation of optically active polyhydroxy compounds, such as synthetic intermediates of monosaccharides, the asymmetric aldol reaction of 1,3-dimethoxy-2-propane (Table 3) by... 

An elegant asymmetric synthesis of frawi-l-(2-hydroxyaryl)-2-trimethylsilylcyclo-propanes 497 of unknown absolute configuration from 2-bromoaryl ethers 496, involving... 

Primary alcohols were oxidised to aldehydes and (less readily) secondary alcohols to ketones by Ru(N0)Cl(salen = )/03//UV (incandescent or halogen lamp), hi competitive experiments between 1- and 2-decanol or benzyl alcohols only the primary alcohol was oxidised [827]. With Ru(NO)Cl(salen )/(Cl2pyNO) or TMPNO or Oj/C H /UV (TMPNO=tetra-methylpyridine-iV,iV -oxide) racemic secondary alcohols were asymmetrically oxidised to ketones [828]. A Ru(NO)(salen " ) complex was used as Ru(N0)Cl(salen " )/02/UV/CgH3Cl to oxidise racemic secondary alcohols to the ketones in the presence of l,3-bis(p-bromophenyl)propane-l,3-dione e.e. of 55-99% were achieved [829], Chiral Ru(NO)Cl(salen ) complexes were made... 

---