Synthesis and properties of a series of sterically hindered guanidine bases

By the reaction of Vilsmeier salts, derived from tetra-alkylureas or from tetra-alkylthioureas, with primary aliphatic amines, a series of sterically hindered penta-alkyl guanidines has been prepared. 2-t-Butyl-1′,1′,3″,3″-tetramethylguanidine and pentaisopropylguanidine combine ease of preparation with a range of resistance to alkylating agents. Preliminary experiments indicate that these inexpensive bases will be useful in organic synthesis.