Camphor and Allied

The enantioselective addition of ally organometallics to carbonyls has become one of the workhorses of organic synthesis. Dennis Hall of the University of Alberta reports (J. Am. Chem. Soc. 125 10160, 2003) the scandium triflate catalysis chiral allylboronic acids become more effective tools. The best of these, the Hoffmann camphor derivative 2, adds to aldehydes under Sc(OTf), catalysis with excellent enantiomeric excess. The reaction works equally well for methallyl, and for the E and Z crotyl boronic acids. The crotyl derivatives react with the expected high diastereocontrol. A limitation to the boronate additions is that branched chain aldehydes give low yields. 

A practical method for the enantioselective addition of an allylic nucleophile to an aldehyde has been acid-mediated ally transfer, as exemplified by the conversion of I and 2 to 3. While this method worked well forcrotyl, allyl transfer itself suffered from eroded ee s. Teck-Peng Loh of the National University of Singapore has found (Tetrahedron Lett. 20 4,45,5819) that camphorsulfonic acid (CSA) mediates this conversion without racemization. The alcohol 1 is prepared by addition of allyl Grignard to camphor, so both enantiomers are readily available. 

The nitration of cellulose became a base for a laige number of empirical efforts to modify cellulose. Louis Menard discovered that tetranitrated cellulose could be dissolved in a mixture of diethyl ether and ethanol (3,4). He labeled the resulting thickened liquid collodion. In the mid 1860 s, John W. Hyatt mixed collodion and camphor (S) to form a hard brittle material he called celluloid. In 1875, Allied Nobel announced the development of blasting gelatin, a combination of collodion and nitrogylcerin. A development which lead to several artificial fabrics occurred when Hilaire de Chaidoimet announced spun cellulose nitrate fabric at the Paris Exhibition in 1889 (6). The material was too flammable to be practical but lead to the development of reprecipitated cellulose, rayon, and cellulose acetate, a common fiber and plastic. 

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