Achiral heptanal

A total of 0.11 g (0.4 mmol) of Ni(cod), is dissolved in 5 ml, of toluene in a lube with a Teflon tap. Then 0.4 mmol of aminophosphinite ligand (D)-FphosNH is dissolved in 5 mL of toluene and 2.0 g of internal standard (heptane or decane) are added. This solution is introduced under N, into the reaction tube and the diene (piperylene) is then added under N2. The tube is then closed and put into a LhermoslalLed bath (40 C) where the solution is stirred with a magnetic stirrer. At the end of the reaction (3 h), the mixture is filtered over silica gel to eliminate the nickel catalyst, and the mixture is analyzed by GC and separated via preparative chromatography and distillation. With 95% conversion of the diene the product contains 16% ( ,Z)-4,5-dimethyI-l,3,6-octatriene (90% ee, NMR) and 12% ( , )-4,5-dimcthyl-l,3,6-octatriene (35 % ee, NMR) besides other (achiral) products. At lower conversions (75% after 0.75 h) the contents of the two chiral isomers are 21 % and 70%, respectively. 

When the enantiomerically enriched alkene (5)-3-methyl-l-hexene is employed, 3-ethyl-l-hexanal is formed with 70% retention of configuration together with 4-methyl-l-heptanal and 2,3-dimethyl-l-hexanal, in spite of the fact that the precursor of this product should be achiral 2-ethyl-l-pentene generated through isomerization of (5)-3-methyl-l-hexene. In order to accommodate this result, a 1,2-hydrogen shift mechanism has been proposed that does not include a true cr carbon-Co bond and is faster than the dissociation of olefin from the olefin-Co complex, which appears to be generally accepted. 

Also, diastereomers of alkenes were enumerated by means of Polya s theorem. Alkanes can be chiral if they have at least seven carbon atoms (there are two isomers of heptane with a stereogenic center, i.e., two pairs of enantiomeric heptanes) if they have at least eight carbon atoms, alkanes can have polychiral diastereomers. The enumeration of stereoisomeric alkanes can be accomplished by means of Polya s theorem achiral alkanes were enumerated for the first time by Robinson et al on applying Polya s theorem and Otter s dissimilarity characteristic equation (review in Ref. 7). 

We performed this difficult study using the Supelco Chirobiotic0 CSPs based on macrocyclic glycopeptide selectors. The system parameters, e, s, a, b, and v, of the four different columns, namely ristocetin, vancomycin, teicoplanin, and teicoplanin aglycon, were obtained for six different normal heptane-ethanol mobile phases and ten different acetonitrile or methanol-water reversed mobile phases [47, 48]. The 44 achiral probe solutes contained aldehydes, ketones, amides, halogenated phenols, nitro-substituted benzenes, and nitro-alkanes. About 2,400 chromatograms were needed to obtain the 5 fl-v system parameters for the 4 CSP columns and the 16 mobile phases [47]. 

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