A novel, easy and mild preparation of sulfilimines from sulfoxides using the Burgess reagent Sadagopan Raghavan * , Shaik Mustafa, Kailash Rathore Organic Division I, Indian Institute of Chemical Technology, Hyderabad 500 007, India article info Article history: Received 27 March 2008 Revised 23 April 2008 Accepted 26 April 2008 Available online 1 May 2008 Keywords: Sulfilimines Sulfoxide Burgess reagent abstract A novel preparation of sulfilimines from the corresponding sulfoxides using the Burgess reagent is described. The reaction is general to dialkyl- and aryl alkyl sulfoxides and proceeds under mild conditions in benzene. A variety of protecting groups can be introduced on the nitrogen of the sulfilimine by choos- ing the appropriate Burgess reagent. Ó 2008 Elsevier Ltd. All rights reserved. Chiral sulfilimines, 1 the nitrogen analogs of sulfoxides, are an interesting class of compounds whose chemistry remains underde- veloped partly because of the limited methods available for their preparation. Chiral sulfilimines have been prepared by kinetic res- olution of racemic sulfilimines, 2 from the corresponding sulfox- ides, 3 and from sulfides by nitrene transfer. 4 In continuation of our interest in the chemistry of sulfilimines, 5 we sought a route to sulfilimines possessing protecting groups that are removable under mild conditions so that they would be synthetically useful as inter- 6 and intramolecular nucleophiles, 5 from the correspond- ing sulfoxides, 7 which are readily available. In connection with another project, to secure cyclohexene derivative 2, we subjected tertiary alcohol 1 to treatment with the Burgess reagent 8 3b under standard conditions. 9 However, TLC analysis did not reveal less polar spot and further analysis indicated that we had not obtained 2 but polar sulfilimine 4 instead (Scheme 1). This discovery prompted us to examine the generality of this transformation and the results of this investigation are reported herein. Initially, racemic methyl p-tolyl sulfoxide 5a was reacted with the Burgess reagent 3a 9f (1 equiv) in anhydrous THF (0.2 M) at 60 °C. After 2 h, sulfilimine 6a was isolated in 30% yield along with unreacted 5a and methyl p-tolyl sulfide (7, Table 1). The use of excess of 3a (2 equiv) relative to 5a led to the com- plete consumption of the latter to furnish 6a in 72% yield along with methyl p-tolyl sulfide 7 in 10% yield. The reaction of 5a with 3a proceeded at rt in both acetonitrile and dichloromethane, with an excess of 3a being required for completion over a 5–7 h period. Interestingly, when the reaction was carried out in benzene, con- version was observed at 0 °C and complete conversion was observed in 5 h to yield 6a in 80% yield. The same reaction at rt was complete within 2 h affording 6a in 85% yield. Having stan- dardized the reaction conditions, 10 the generality of the procedure was examined employing a variety of aryl alkyl and di-alkyl sulfox- ides (Table 2). A perusal of Table 2 reveals that the reaction is gen- eral, high yielding and proceeds under mild conditions. The reaction proceeds with equal facility on sulfoxides with electron 0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2008.04.152 * Corresponding author. Tel.: +91 040 27160123; fax: +91 040 27160512. E-mail addresses: sraghavan@iict.res.in, purush101@yahoo.com (S. Raghavan). OH S p-Tol O OH S p-Tol NCO 2 Me S p-Tol O 3b, THF 3b, THF 1 2 4 Scheme 1. Tetrahedron Letters 49 (2008) 4256–4259 Contents lists available at ScienceDirect Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet