Di-tert-butyl Dicarbonate and 4-(Dimethylamino)pyridine Revisited. Their Reactions with Amines and Alcohols1

Abstract

The reaction of BOC₂O in the presence and absence of DMAP was examined with some amines, alcohols, diols, amino alcohols, and aminothiols. Often, unusual products were observed depending on the ratio of reagents, reaction time, polarity of solvent, pK_a of alcohols, or type of amine (primary or secondary). In reactions of aliphatic alcohols with BOC₂O/DMAP, we isolated for the first time carbonic−carbonic anhydride intermediates; this helps explain the formation of symmetrical carbonates in addition to the O-BOC products. In the case of secondary amines, we succeeded to isolate unstable carbamic−carbonic anhydride intermediates that in the presence of DMAP led to the final N-BOC product. The effect of N-methylimidazole in place of DMAP was also examined.