Kazuaki Ichikawa

Olefin metathesis and side reactions with the binary systems of WCI6 and metal alkyls

Abstract The comparison of the behaviors of the WCl6-metal alkyl systems (metal alkyls are Bu4Sn, Et2Zn, Et3Al, and BuLi) was carried out in the metathesis of 2-heptene in benzene. The WCl6Et2Zn and the WCl6BuLi systems showed the sharp dependence of metathesis on the co-catalyst/WCl6 ratio, whereas the WCl6Bu4Sn and the WCl6Et3Al systems did the dull one. The yield of the Friedel-Crafts products, heptylbenzenes, increased with a decrease in the co-catalyst/WCl6 and the olefin/WCl6 ratios, though the WCl6BuLi system barely catalyzed this side reaction. A proper amount of dicyclopentadiene, phenylacetylene, ethyl ether, ethanol, and esters repressed the Friedel-Crafts reaction, and the metathesis products were obtained in high yield and high selectivity in the metathesis of 2-heptene catalyzed by the WCl6Bu4Sn system.

The mechanism of catalyst formation from tungsten hexachloride and cocatalyst in olefin metathesis

SummaryThe mechanism of the catalyst formation in hept-2-ene metathesis was investigated by gas chromatographic analysis of the products from reactions of tungsten hexachloride with R4Sn(R = Ph, n-Bu), RLi, RMgl (R = n-Bu) or R3Al(R = Et) as cocatalyst. The products are chiefly RH, RCl and RR species, and the highest catalytic activity is observed for an equimolar ratio of products to tungsten hexachloride. The facts suggested that the active catalyst, a WCl4 species, is formed by the elimination of two R groups from R2WCl4 and/or one R group and chlorine from RWCl5. The total quantity and composition of the products varies with the cocatalyst:WCl6 ratio, and the difference between the behavior of tetra-n-butylstannane and n-butyllithium in the catalyst formation is explainable on the basis of their relative nucleophilicities. Gas chromatographic analysis of the organotin compounds resulting from the WCl6:: Bu4Sn system shows that tetra-n-butylstannane provides only one butyl group per mole of WCl6.

Steric Structures of Triacylglycerols in the Seed Oil of Carrot Daucus carota L. var. sativa DC.

The steric structures of the triacylglycerols (TGs) in the seed oil of carrot Daucus carota L. var. sativa DC. were studied by the stereospecific analysis of the acyl distributions using the chiral-phase high-performance liquid chromatography of the monoacylglycerol derivatives. Total fatty acids of the seed oil TGs contained 71 mol % petroselinic acid (6-18 : 1), 12 mol % oleic acid (9-18 : 1), 11 mol %linoleic acid (18 : 2 n-6), and 4 mol % palmitic acid (16 : 0). Fatty acid percents in each sn-1, sn-2 and sn-3 position of the TGs were 6-18 : 1 (38, 23 and 40 %), 9-18 : 1 (21, 66 and 13 %), and 18 : 2 n-6 (20, 65and 15 %). Structures and estimated contents of the major TG components in the carrot seed oil wasfound to be (6-18 : 1) (6-18 : 1) (6-18 : 1) 3248 %, (6-18 : 1) (9-18 : 1) (6-18 : 1) 1725 %, (6-18 : 1) (18 : 2 n-6) (6-18 : 1) 1522 %. Petroselinic acid distributes preferentially at the sn-1 and sn-3 positionsin the carrot seed oil TGs in analogy with 16 : 0 and 18 : 0 in the ordinary seed oil TGs.