Camille and Henry Dreyfus Foundation

The Camille & Henry Dreyfus Foundation, chartered in 1946 by Camille Dreyfus as a tribute to his brother and partner in science, Henry, hosted Climate, Energy, and the Changing Environment: A Dreyfus Foundation Symposium on Environmental Chemistry Research, at the New York Academy of Sciences in October 2008. After having awarded ca. 100 fellowships, it seemed an appropriate time to assess the status of this rapidly growing field.magnified image

Maureen Scharberg's letter “Importance of teaching” ([24 May, p. 1086][1]) appears to miss the point of the News article about the National Science Foundation (NSF) report ([1][2]) on undergraduate education (J. Mervis, [19 Apr., p. 345][3]). The issue raised by the report has nothing to do with

Lewis acid-promoted reactions of α-diazocarbonyl compounds with nitriles provide a general method for the production of oxazoles in high yields.Because of the relative absence of α-halogenation products in reactions performed with BF₃.Et₂O, this Lewis acid is preferred when the nitrile is employed as the reaction solvent.Reactions of diazoketones in nitrile solvents generally result in higher oxazole yields (70-99%) than do reactions of N₂CH₂CO₂Et (26-31%).When these transformations are performed at or below room temperature, at least 1 equivalent of the Lewis acid is required, although catalytic activity is observed in reactions performed at 65°C.In BF₃.Et₂O promoted reactions, a min. 10-fold molar excess of nitrile is required for optimum oxazole production, although use of SbF₅ results in high yields of oxazoles even when only a 3-fold excess of the nitrile is employed.The mechanism for oxazole formation apparently involves initial activation of the nitrile through association with the Lewis acid, followed by attack of the nitrilium complex at the carbonyl O of the diazocarbonyl compound and internal displacement of N.Although Lewis acid association with the diazocarbonyl compound is the more favorable process in reactions performed with equivalent amounts of nitrile and diazocarbonyl compound, only equilibrium association of the Lewis acid with the nitrile effectively leads to oxazole formation.