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A study was conducted to examine the role of Grignard reagents in the regioselective synthesis of protected polyhydroxy-compounds with only one hydroxy group. The stereochemistry of the carbon center was found to be either syn or anti to the acetal oxygen moiety at the C-O bond cleavage location. The difference in reactivity has also been found in the reaction of trisacetonide of sorbitol with MeMgI.

The applications of 1,4-di-O-tert-alkyl-L-threitols as chiral auxiliaries in the asymmetric nucleophilic addition of alkyllithiums to hydrazones are investigated. Chiral acetal-hydrazones 9, obtained from the chiral acetals 8 by ozonolysis followed by treatment with dimethylhydrazine, are allowed to react with organolithium reagents in toluene at - 78 [degrees] C to give 15 with excellent diastereoselectivity. The stereochemical assignments were based on the X-ray crystal structure of 17a. The absolute configuration at [C.sub.2] of the major isomer of the adducts 15 was thereby determined to be S. The nucleophile thus attacked from the si face of the C = N moiety. The effect of solvent on the diastereoselectivity of the reactions of 9 with organolithium reagents is reported. Polar aprotic solvent shows poor diastereoselectivity, and the diastereoselectivity is reversed when the reaction is carried out in THF. Reaction of dl-14 with methyllithium has been studied for comparison purposes and the reaction shows the opposite selectivity. Chelation intermediates 18 and 26 are proposed for these reactions to account for the observed stereoselectivities.

Reactions of ortho esters of myo-inositol with 1-2 equiv of Grignard reagents in benzene-ether produced regio- and stereoselectively the corresponding ring opening products having a free hydroxy group at C-1. The regioselectivity was rationalized because of the presence of the 2-methoxy group which functioned as an auxiliary to create a chelation complex with magnesium. Inositol derivatives with two free hydroxy groups at C-1 and C-3 positions can be formed from reactions of compound 6 or 8 with excess Grignard reagents or under more drastic conditions.

Bis‐norbornene and bis‐cyclobutene with different kinds of linkers have been extensively used for the synthesis of double stranded ladderphanes under ruthenium‐ or molybdenum‐catalyzed ring opening metathesis polymerization (ROMP) conditions. The key to the success relies on the selective formation of comb‐like polynorbornenes or polycycloubtenes, where pendants are all aligned towards similar direction. This minireview summarizes various methods (chemical methods, spectroscopic means, and nonlinear optical measurements) for determining the comb‐like conformations of pendants on these rigid‐rod polymers. The approach is based on the proximal relationship between adjacent pendants. Interactions between these adjacent pendants would enable a change in chemical reactivity [ABSTRACT FROM AUTHOR]

A method for the synthesis of chiral bisazafulleroids with a C2 chiral auxiliary was developed based on the reaction of chiral 1,4-tert-alkoxy-2,3-bisazidobutanes with C60. The synthetic strategy involves the formation of bismesylates by the reaction of C2 chiral diols with MsCl and Et3N. An intermediate product was formed by the reaction of bismesylates with NaN3 and DMF/H2O in the presence of 15-crown-5. The chiral bisazafulleroids were produced by the reaction of the intermediate product with C60 and chlorobenzene.

A method for the synthesis of chiral bisazafulleroids with a C2 chiral auxiliary was developed based on the reaction of chiral 1,4-tert-alkoxy-2,3-bisazidobutanes with C60. The synthetic strategy involves the formation of bismesylates by the reaction of C2 chiral diols with MsCl and Et3N. An intermediate product was formed by the reaction of bismesylates with NaN3 and DMF/H2O in the presence of 15-crown-5. The chiral bisazafulleroids were produced by the reaction of the intermediate product with C60 and chlorobenzene.

The use of tunable diols obtained from the reaction of bisketals of L-threitol with Grignard reagents as a chiral auxiliary in asymmetric Simmons-Smith cyclopropanation was examined. Specifically, the impact of modifications to the size of the alkoxy substituent on the chelating reactivity and diastereoselective cyclopropanation of chiral ketals of cyclic enones were investigated.

We report the carrier transport properties of a furan-containing oligoaryl PF6, which contains no arylamine moiety in the molecular structure but exhibits competitive hole-transport capability in comparison with conventional arylamine-based hole-transport materials often used in organic light-emitting devices (OLEDs) and xerography. Thin films of this compound exhibit both morphological stability and appropriate energy levels for OLED applications. OLEDs using PF6 as the hole-transport layer show low turn-on voltage, high efficiency, and high brightness competitive with those using conventional hole-transport materials, strongly indicating superior hole-transport properties of PF6. The carrier mobility of PF6 was directly measured by the time-of-flight transient photocurrent technique under various temperatures and electric fields. Nondispersive hole transport was observed and a room-temperature hole mobility in excess of 10[sup -3] cm[sup 2]/V s was obtained under high fields. The field and temperature dependence of hole mobility were analyzed and were found consistent with the Bässler (disorder) formalism. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

2-aryl-1,3-(bistrimethylsilyl)propenes are of interest because of their 1,3- and 3,3-propene dianion synthons. Their reactions with such electrophiles as N-bromosuccinimide (NBS) are invariably stereoselective even when the starting materials are an isomeric mix. With NBS, for example, the E and Z isomers yield the Z-dibromo or monobromopropenes. The resulting alpha-haloallylsilanes also react stereoselectively with NBS, 1,1-diethoxyethane and hexanoyl chloride. The results show that 1,3-silylpropenes behave as two interactive allyl silanes and act effectively as dianion synthons.