The regioselective esterification of cellulose by reaction with bulky acyl halides including pivaloyl chloride, adamantoyl chloride and 2,4,6-trimethylbenzoyl chloride was studied. Functionalization conditions to achieve a given degree of substitution (DS) and the resulting ester substitution pattern were described in detail. One-and twodimensional NMR spectroscopy techniques were used to confirm the structure of the esters obtained. We compared the effects on substitution of using different esterifying reagents and solvent systems including DMAc/LiCl, DMSO/TBAF, and ionic liquids (ILs).
Photolysis, thermolysis,, Vmax (KBr disc) 1655 (C = O ) , fer of 1-benzoylcycloheptatriene are described.1050 cm-l (BF,), T (trifluoroacetic acid, Me4Si external
The reaction of cycloheptatriene with acyl halides in the presence of a Lewis acid does not involve a hydride-atom> transfer. The reaction has been used to prepare two series of compounds, ( a ) benzyl ketones, and (b) l-acylcycloheptatrienes. An intermediate common to both reactions has been identified, allowing a coherent mechanism to be postulated.Hydride-atom Transfer. --Cycloheptatriene undergoes a hydride-atom transfer reaction to give the tropylium ion. This was used to synthesise tropylium fluoroborate in almost quantitative yield from cycloheptatriene and trityl fluoroborate.l described the reaction of cycloheptatriene with t-butyl halides and a Lewis acid to give the corresponding tropylium salts in ca. 20% yield. They claimed these salts were formed by halidehydride exchange but did not detect t-butane.Harmon et aL3 discussed the reaction of cycloheptatriene with boron halides to form the tropylium ion. Hydride-atom transfer reactions and electrophilic attack on the triene system were considered as possible mechanisms.The acyl fluoride-Lewis acid fluoride complexes described by Olah4 are extremely reactive. It was hoped that they would be hydride-acceptors in lowtemperature reactions, as in Scheme 1.
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