Olefination of N-Sulfinylimines under Mild Conditions

Olefins are ubiquitous building blocks in many naturally occurring bioactive molecules and important reactive intermediates in numerous organic transformations.¹A plethora of organic transformations have been invented for the stereo-controlled construction of substituted alkenes.² Importantly, new approaches for the synthesis of olefins are still being investigated, as transformation of different functional groups into olefins may be key in the total synthesis of natural compounds, drugs etc. Sulfinyl groups have an important role as chiral auxiliaries in nucleophilic addition reactions. Therefore, N-sulfinylimines have been attracting much interest owing to their simple preparation and inherent reactivity. Here, we demonstrate a simple and efficient diastereoselective transformation of this chiral directing group into useful 1,2-disubstituted alkenes, which can be further functionalized as required. Different aryl phosphonates reacted with a range of electronically diverse N-sulfinylimines to afford in greater than 99:1 E-alkenes in almost every case. The most important feature of this protocol is that the reaction can be performed at room temperature using inexpensive sodium hydride as the most effective base to generate the reactive phosphonate ylide producing E- alkenes in high yields.

Reference:

1)Comprehensive Natural Products Chemistry, vol. 1–9 (Eds.: D. Barton, K. Nakanishi), Elsevier, New York, 1999.

2)Williams, J. M. J. Preparation of Alkenes: A Practical Approach; Oxford University Press: Oxford, UK, 1996. (c) Kelly, S. E. In ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, UK, 1991; Vol. 1, p 729.