Choon-Hong Tan and Juan Shen
Electronic Encyclopedia of Reagents for Organic Synthesis (e-EROS) , 2008, DOI: 10.1002/047084289X.rn00967. Article Online on September 15, 2008. (Invited)
Abstract: 2,3,5,6‐Tetrahydro‐2,6‐bis(phenylmethyl)‐1H‐imidazo[1,2‐a]imidazole was prepared from (S)‐phenylalaninol in five steps (eq 1).2 This method was also used to prepare several other chiral bicyclic guanidines. The catalyst was prepared as the guanidinium iodide. Before use the catalyst is basified with K2CO3: the guanidinium salt was dissolved in CH2Cl2 and loaded onto a column packed with solid K2CO3 from which the free base was eluted with CH2Cl2.
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