Ring opening boron trifluoride catalyzed

Cycloadduct 212 is converted into the dihydrobenzofuran 213 when treated with boron trifluoride diethyl etherate in good yield <2000JA8155>. The formation of the dihydrobenzofuran proceeds by an initial ring opening followed by a subsequent dehydration and acid-catalyzed cyclopropyl ketone rearrangement (Equation 142). 

Polyformaldehyde. Polyformaldehyde or polyacetal is made by two different processes. Delrin is made from formaldehyde by anionic polymerization catalyzed by a tertiary amine. The homopolymer is end-capped with acetic anhydride. Celcon is made from trioxane cationic copolymerization using boron trifluoride catalyst and ethylene oxide (2-3%) as the comonomer. Boron trifluoride is a Lewis acid that associates with trioxane and opens up the six-membered ring. Ethylene oxide provides the end capping. Without an end cap, polyformaldehyde is thermally unstable and loses formaldehyde units. 

PO also reacts with active hydroxyl hydrogen derived from the ring opening of other compounds such as EO and tetrahydrofuran thus, a copolymer polyol is obtained. Typically, polyols are obtained from base-catalyzed reactions with aqueous ammonia, sodium or potassium hydroxide, or lower alkyl tertiary amines such as trimethyl- and triethylamine. The reaction of PO with tetrahydrofuran is catalyzed by boron trifluoride etherate. The molecular weights of polyols prepared according to the reactions described earlier range from 200 to 7000. 

Boron trifluoride is a highly moisture-sensitive gas (31). It is utilized in esterification, ether formation, Friedel-Crafts alkylation and acylation, and Lewis acid-catalyzed Diels-Alder reactions. A more widely used, easy-to-handle and convenient liquid source of BF3 is boron trifluoride etherate [BF3-0(C2H5)2] (32). Its main usage as catalyst is in the direct esterification of all types of acids, rearrangements, aldol condensation, and Lewis acid-catalyzed Diels-Alder reactions. It is the most frequently used acid in epoxide ring opening and rearrangement (33). 

The most common polymer family to be attached to sohd inorganic materials is aliphatic polyesters, such as poly(E-caprolactone) (PCL). PCL is a thermoplastic, bioresorbable (via hydrolysis), and semicrystalline polymer that is synthesized by the ring-opening polymerization (ROP) of s-caprolactone monomer (Khan et al., 2010). As depicted in Fig. 3.2(e), this in situ polymerization scheme can be catalyzed by tin(II)2-ethylhexanoate(Sn(Oct)2) or boron trifluoride dimethyletherate(BF30(CH3)2)... 

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