In epoxide ring opening

The second method nses the same reagents in the presence of a base and consists of initially making 3-(l-naphthyloxy)propylenoxide (12.1.3), the snbseqnent reaction with iso-propylamine which resnlts in epoxide ring opening leading to the formation of propranolol (12.1.2) [1-6]. 

Rough guidelines for the prediction of regioselectivity in epoxide ring openings are summarized in Scheme 4.60. Under neutral or basic reaction conditions alkyl-or aryl-substituted epoxides react with most nucleophiles at the less substituted carbon atom [248-253]. Under acidic reaction conditions, however, product mixtures or preferential attack at the most substituted carbon atom can be observed. Acids can usually be used to enhance the reactivity of epoxides and to promote substitution at the site of an epoxide which forms a carbocation more readily. 

High dilutions reduced the amount of oligomers formed. Preliminary experiments on enantio-enriched hydroxyl esters 20.6 and 20.7, using distannoxane transesterification catalyst, produced stereochemically diverse homo- and heterodimers 20.8-20.10. Functionalization of the macrodiolides was investigated in an effort to create additional structural diversity. Electrophilic epoxidation of macrodiolide 20.9 afforded bis-epoxide 20.11. Further diversification was achieved by treating the macrodiolide bis-epoxide with DBU, which resulted in epoxide ring opening to afford a,P-unsaturated macrolide 20.12. 

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). 

Oxiranecarboxylic acids 41 (glycidic acids) can be converted into a,P epoxy diazomethyl ketones 42 via mixed anhydrides. It was found that photolysis of these compounds in the presence of alcohols gave yhyunsaturated esters 44. It is thought that nucleophilic attack of the alcohol on the ketene 43 results in epoxide ring opening. The E olefin isomer is predominately formed, although small quantities of Z esters are also isolated (< 10%). Conveniently non-racemic, chiral substrates are readily prepared via Sharpless asymmetric epoxidation of allylic alcohol 39, followed by... 

Finally, the catalytic activity of DMCs in esterification reactions can be readily combined with their catalytic activity in epoxide ring-opening polymerizations, as was reported by Suh et al. [35]. This study showed that the copolymerization of propylene oxide with cyclic acid anhydrides such as succinic, maleic, or phthalic anhydride, catalyzed by a Zn-Co-DMC, afforded polyester polyols characterized by a moderate molecular weight and narrow polydispersity index. 

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