[39509-34-7] · C10H21BF4N2 · N-Methyl-N,N´-di-t-butylcarbodiimidium Tetrafluoroborate · (MW 256.14)
Physical Data: mp 85-86 °C.
Form Supplied in: colorless hygroscopic crystals.
Preparative Method: N,N-di-t-butylcarbodiimide (1 equiv) is added dropwise to 1 equiv of Trimethyloxonium Tetrafluoroborate at 0 °C and stirred for 6 h before warming to rt and stirring for an additional 18 h. Isolation under fairly anhydrous conditions gives the diimidium salt in 62% yield.1
The reagent has been used in dehydrative coupling processes.2 For example, diols (1) may be dehydratively cyclized to ethers by 1.0 equiv of the diimidium salt (2) and slightly more than 1 equiv of Triethylamine (eq 1) to give the corresponding cyclic ether and the urea (3). Yields vary and examples of ring sizes larger than seven members formed in the process have not been reported.
Appropriately protected amino acids have been coupled to dipeptides (eq 2). There is no apparent reason to favor this reagent over others in this process.
Kim F. Albizati
University of California, San Diego, CA, USA