The first synthesis of pyridinium N-benzoylguanidines by bismuth- and mercury-promoted guanylation of N-iminopyridinium ylide with thioureas Silvio Cunha, a, * Manoel T. Rodrigues Jr., a Cleuza C. da Silva, b Hamilton B. Napolitano, c Ivo Vencato d and Carlito Lariucci d a Instituto de Quı ´mica, Universidade Federal da Bahia, Campus de Ondina, Salvador-BA 40170-290, Brazil b Departamento de Quı ´mica, Universidade Estadual de Maringa ´, Av. Colombo 5720, Maringa ´-PR 97020-900, Brazil c Cie ˆncias Exatas e Tecnolo ´gicas, Universidade Estadual de Goia ´s, BR 153, Km 98, 75001-970, Ana ´polis-GO, Brazil d Instituto de Fı ´sica, Universidade Federal de Goia ´s, CP 131, 74001-970, Goia ˆnia-GO, Brazil Received 31 January 2005; revised 8 August 2005; accepted 11 August 2005 Available online 2 September 2005 Abstract—This work describes the first successful synthesis of five pyridinium N-benzoylguanidines. These new pyridinium ylides were prepared in moderate to good yields through the guanylation reaction of N-iminopyridinium ylide with N-benzoylthioureas, using both bismuth nitrate and mercury chloride as inorganic thiophiles. X-ray analysis of one pyridinium N-benzoylguanidine was investigated and the E configuration assigned. Intermolecular interactions of the type C–H/O and C–H/p were observed in the solid state. The results related in this study represent the first description of a ylide as the nucleophilic partner in the guanylation reaction. q 2005 Elsevier Ltd. All rights reserved. 1. Introduction The synthesis of polysubstituted guanidines is a field of intense investigation 1 owing to the presence of guanidinium group in diverse biologically active substances, 2 mainly pharmaceutical compounds with a broad spectrum of activity. 3 To the synthesis of a guanidine-containing compound two general strategies are possible according to Batey and co-workers: a guanidinylation reaction or a guanylation reaction. 4 In the first, a pre-formed guanidine is modified/functionalized (for instance, through N-alkylation, N-acylation or transamination), and in the latter, typically, a nucleophilic amine is reacted with a electrophilic amidine species (or a carbodiimide equiv). Typical electrophilic reagents employed in guanylation reaction are indicated in Figure 1. 5 Our research group has continued interest in the area of bismuth- and mercury-promoted guanylation reaction of amines with thioureas in search for new polysubstituted guanidines. Previously, we had described the activation of thioureas by the N-benzoyl group in the HgCl 2 -promoted guanylation. 6 Later, we extended this guanylation reaction to the bismuth approach, whereby Bi(NO 3 ) 3 was employed in the same reaction, being the first description of a bismuth- promoted guanylation of thioureas. 7 While a broad spectrum of amine has been investigated in guanylation methodologies, the use of more functionalized nitrogen nucleophiles is scarce. 8 The preparation of pyridinium N-ylides 9 and their use in the synthesis of nitrogen-containing heterocycles 10 such as 2-aminoazines, 2-aminoazoles, imidazopyridines and tetra- hydropyridines has attracted the attention in recent years. 11 Tetrahedron 61 (2005) 10536–10540 0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2005.08.052 Figure 1. Typical guanylating reagents. Keywords: Pyridinium; Guanidine; Bismuth. * Corresponding author. Tel.: C55 71 2375784; fax: C55 71 2374117; e-mail: silviodc@ufba.br