These facts lead to extensive efforts for the synthesis of this class of acylguanidines. Herein, we wish to report a simple method to access N-acyl-N′-substituted guanidines by condensation of N-acyl-N′-substituted thiourea 1 with hexamethyldisilazane (HMDS) as a nitrogen source under the mild reaction conditions (Scheme 1). ... With the optimized reaction conditions in hand, the scope and limitation of this method were examined (Scheme 3, Table 2). ...