Boron Trifluoride Etherate Links

It was projected that compound 13 could be stereoselectively linked, through its free phenolic hydroxyl group, with the anomeric carbon of intermediate 12 under suitably acidic conditions (see Scheme 8). Gratifyingly, the action of boron trifluoride etherate on a mixture of 12 and 13 in CH2CI2 at -50 °C induces a completely stereoselective glycosidation reaction, providing the desired a-ano-mer 48 in an excellent yield of 95 % from 46. It is presumed that boron trifluoride initiates cleavage of the anomeric trichloroacetimi-... 

Reaction of the benzotriazole-linked aminopyridine 503 with 2,3-dihydrofuran and boron trifluoride etherate results in cyclization to the furopyridopyrimidinium salt 504 with loss of benzotriazole (Equation 221) <1998S704>. 

Research in the laboratory of H.M.I. Osborn showed that the use of cyclohexene derivatives as nucleophiles in the Lewis acid-mediated Type I carbon-Ferrier reaction of 3-0-acetylated glycals can be used to prepare unsaturated 3-linked C-disaccharides. The incorporation of the alkene took place with one equivalent of glucal in the presence of boron-trifluoride etherate in 33% yield. The desired C-disaccharide was obtained by selective hydrogenation of the exocyclic double bond in the presence of an endocyclic one. 

Chloro-2-hydroxypropyl derivatives of such polysaccharides as cellulose and cross-linked dextran (Sephadex) may be prepared by treatment with epichlorohydrin in boron trifluoride etherate. These 3-chloro-2-hydroxypropylated polysaccharides may, in turn, react with ammonia, or primary, secondary, or tertiary amines, and the resultant derivatives of cellulose and Sephadex LH-20, particularly an 0-[3-(di-butylamino)-2-hydroxypropyl] derivative of the latter, are useful anion-exchangers. In the amination procedure, between 50 and 100% of the chlorine atoms are utilized, except in the reaction with tertiary... 

A synthesis of 1,2-O-isopropylidene-a-D-ribofuranose from l,3,5-tri-C)-benzoyl-a-D-ribofuranose has been described. The kinetic products of isopropylidenation of D-galactose, D-allose, and D-talose have been shown to be the 4,6-linked isomers in 67, 81, and 93% yield respectively. A shorter synthesis of 1,2-0-iso-propylidene-a-D-galactofuranose by hydrolysis of the 1,2 5,6-di-O-isopropylidene ketal with 40% acetic acid is reported. The product was converted into 1,2-0-isopropylidene-jS-L-arabinofuranoside by sequential periodate oxidation and borohydride reduction. Treatment of l,2-f -isopropylidene-glycofuranoses with boron trifluoride etherate in benzene has been shown to lead to dimeric dianhydrides, e.g., the 3,5-di-O-benzoyl-xylose derivative (1) (Scheme 1). ... 

Low-molar-mass poly(butadiene) oils with 80%-97% cw-1,4 contents are produced with other Ziegler catalysts (for example, cobalt compounds with alkyl aluminum chlorides or nickel compounds with trialkyl aluminum and boron trifluoride-etherate). The products have few cross-links and dry as fast as wood oil and faster than linseed oil. Conversion of the poly (butadiene) oils with 20% maleic anhydride gives air-drying (air-hardening) alkyd resins. Modified poly (butadiene) oils stabilize erosion-endangered soils. Because of its low viscosity, the aqueous emulsion penetrates the surface soil layers. The surface crust is reinforced by an oxidative bonding process. Since no skin is formed on the soil crust, the aqueous absorption characteristics of the soil are retained. 

Because the monomer is a diepoxide, a three-dimensional lattice results. A similar three-dimensional product forms from reactions with other cross-linking materials, like boron trifluoride-etherate, boron... 

It was reasoned, therefore, that if a bifunctional spiro ortho ester could be prepared and a small amount of this bifunctional material were to be copolymerized with the l,4,6-trioxaspiro[4.4] nonane (I), a lightly cross-linked elastomeric material could be produced with essentially no change in volume. Model compounds showed that phenyl glycidyl ether would condense with Y bwtyro-lactone to produce a substituted spiro ortho ester in a 50% yield and that this material would indeed polymerize at 30" in the presence of boron trifluoride etherate. 

For the first time, a preformed nonmacrocyclic cobalt(III) tris-dimethylglyoximate was cross-linked with boron trifluoride in diethyl ether [2] ... 

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