Asymmetric 1 -octene

Early attempts at an asymmetric hydroalumination utilized a chiral -butylsalicylidenime complexed to a nickel(n) complex 117.128 When racemic 3,7-dimethyl-1-octene 116 was treated with 0.2mol% of the nickel complex 117 and 0.3 equiv. of TIBA at 0°C, followed by hydrolysis, the alkene 118 with 1.2% ee was obtained. The unreacted olefin 119 was recovered and found to have an ee of 1.8% (Scheme 14). 

ASYMMETRIC HYDROGENATION OF ALLYLIC ALCOHOLS USING BINAP-RUTHENIUM COMPLEXES (S)-(-)-CITRONELLOL (6-Octen-1-ol, 3,7-dimethyl, (S)-)... 

The male produced aggregation pheromone of the Colorado potato beetle, Lepitnotarsa decemlineata, (5)-l,3-dihydroxy-3,7-dimethyl-6-octen-2-one and its (f )-isomer were synthesized using lipase-catalyzed asymmetric acetylation of +)-2,... 

A special case of asymmetric enantiomer-differentiating polymerization is the isoselective copolymerization of optically active 3-methyl-1-pentene with racemic 3,7-dimethyl-1-octene by TiCl4 and diisobutylzinc [Ciardelli et al., 1969]. The copolymer is optically active with respect to both comonomer units as the incorporated optically active 3-methyl-l-pentene directs the preferential entry of only one enantiomer of the racemic monomer. The directing effect of a chiral center in one monomer unit on the second monomer, referred to as asymmetric induction, is also observed in radical and ionic copolymerizations. The radical copolymerization of optically active a-methylbenzyl methacrylate with maleic anhydride yields a copolymer that is optically active even after hydrolytic cleavage of the optically active a-methylbenzyl group from the polymer [Kurokawa and Minoura, 1979]. Similar results were obtained in the copolymerizations of mono- and di-/-menthyl fumarate and (—)-3-(P-styryloxy)menthane with styrene [Kurokawa et al., 1982],... 

The use of chiral azomethine imines in asymmetric 1,3-dipolar cycloadditions with alkenes is limited. In the first example of this reaction, chiral azomethine imines were applied for the stereoselective synthesis of C-nucleosides (100-102). Recent work by Hus son and co-workers (103) showed the application of the chiral template 66 for the formation of a new enantiopure azomethine imine (Scheme 12.23). This template is very similar to the azomethine ylide precursor 52 described in Scheme 12.19. In the presence of benzaldehyde at elevated temperature, the azomethine imine 67 is formed. 1,3-Dipole 67 was subjected to reactions with a series of electron-deficient alkenes and alkynes and the reactions proceeded in several cases with very high selectivities. Most interestingly, it was also demonstrated that the azomethine imine underwent reaction with the electronically neutral 1-octene as shown in Scheme 12.23. Although a long reaction time was required, compound 68 was obtained as the only detectable regio- and diastereomer in 50% yield. This pioneering work demonstrates that there are several opportunities for the development of new highly selective reactions of azomethine imines (103). 

The bicyclo[3.3.0]octene skeleton is of interest due to its potential use as an intermediate in the synthesis of cyclopentanoid natural and nonnatural compounds. The bicyclo[3.3.0]octene skeleton can be prepared by asymmetric elimination of the corresponding alcohols on treatment with a variety of chiral amines80, S1. Bicyclic trifluoromethanesulfonales 1 on treatment with (5)-Ar,Ar-dimethyl-l-phenylethylaminc give the corresponding bicyclo[3.3.0]octenes 2 with 15,5/ -configuration with up to 89% enantiomeric excess in high yield. 

As shown in Table 22 in most examples, the prevailing absolute configuration of the asymmetric carbon atoms of the lateral chains of the first eluted fractions is opposite to the one of the support this indicates that the polymer having the same structure as the support is more strongly adsorbed. However, this is not a general phenomenon, as it is shown by the chromatography of poly-3.7-dimethyl-l-octene obtained from the racemic monomer using poly-(S)-3-methyl-l-pentene as support (118). 

Figure 1.9 Examples of a chemoselectivity and diastereoselectivity in the oxidation of a-pinene, b regioselectivity in the hydroformylation of 1-octene, and cenantioselectivityin the hydrogenation of the prochiral isopropyl (2-methoxyisopropyl) imine ( indicates the asymmetric carbon atoms).

As a consequence of the restricted jump-rope rotation around the trans double bond, (i j-cyclo-octene 38E is chiral. Optically active (E)-cyclo-octene has long been known, but the conventional multistep synthesis is rather tedious [138-140]. In contrast, direct-preparation of optically active (Ej-cyclo-octene through asymmetric photosensitization is an attractive alternative. The first enantiodifferentiating Z-E photoisomerization of cyclo-octene 38Z sensitized by simple chiral alkyl benzenecarboxylates was reported in 1978 to give low enantiomeric excesses (ee s) of <6% [141] a variety of systems and conditions have been examined since then to raise the product ee. For an efficient transfer of chiral information... 

Crucially, not only temperature [148,149] but also other environmental factors, such as pressure [143], magnetic/electronic fields [150,151], and solvent [152] play vital roles in a variety of asymmetric photochemical reactions. In the enantiodifferentiating photoisomerization of (Z cyclo-octene 38Z, (7 )-(—)-( ,)-38E is produced predominantly at temperatures higher than the isoenantiodifferentiating temperature (r0), while the antipodal (S)-(+)-isomer prevails at temperatures lower than T0 even if... 

Asymmetric photoisomerization of cyclo-octene was also investigated in supramolecular systems such as native [153] and modified cyclodextrins [154,155], chirally-modified zeolite [156], and DNA grooves [157]. 

Moreover, cyclization of(Z)-2-methyl-5-octen-l-ol (3) leads mainly to the 2.5-rran.s-disubstituted tetrahydro-2//-pyran with high 1,4-asymmetric induction and the diequatorial arrangement is preferred81. 

The preparation of alkenic alcohols based on rDA processes has found application in the synthesis of natural products. Matsutake alcohol (14a (-)-( )-l-octen-3-ol), an important flavor component of mushrooms, can be prepared in high enantiomeric purity by a method that includes rDA cleavage as a key step. Asymmetric DA addition gave enantiomerically pure adducts that were modified dia-... 

Sih (38) has described the reduction of E-l-iodo-l-octen-3-one with Penicillium decumbens to give the desired S-alcohol. Based on optical rotation, the e.e. was about 80%, An asymmetric chemical reduction of this same ketone, using lithium aluminum hydride that had been partially decomposed by one mole each of S-2,2 -dihydroxy-l,T-binaphthol and ethanol (42), gave the desired alcohol in 97% e.e. This reagent also reduced l-octyn-3-one in 84% e.e. to the corresponding alcohol (43). A 92% e.e. could be obtained with B-3-pinanyl-9-borabicyclo[3.3.1]nonane as the reducing agent (44). 

Enders, D., Baus, U. Asymmetric synthesis of both enantiomers of (E)-4,6-dimethyl-6-octen-3-one, the defensive substance of daddy longlegs, Leiobunum vittatum and L. calcar (Opiliones). Liebigs Ann. Chem. 1983, 1439-1445. 

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