Chlorophosphonium salts (CPS) have recently emerged as useful synthetic intermediates in phosphorus chemistry.1,2,3 In most cases,4 the CPS is generated by treatment of the phosphine oxide with oxalyl chloride. We now present evidence that there is a previously unsuspected interaction of the CPS with its precursor oxide, which was uncovered in the reaction of CPS with chiral non-racemic alcohols. The pair of diastereomeric alkoxyphosphonium salts (DAPS), formed undergoes Arbuzov collapse to give enantioenriched phosphine oxides.5 It was found that, if the CPS is allowed to interact with the scalemic phosphine oxide, there is erosion of its ee. This stereomutation was intensively investigated using independently generated CPS and a mechanism involving formation of a POP species is proposed.  References:  [1]       (a) R. M. Denton, J. An, B. Adeniran, Chem. Commun. 2010 , 3025�3027;  (b) R. M. Denton, J. An, B. Adeniran, A. J. Blake, W. Lewis, A. M. Poulton, J. Org. Chem. 2011 , 76, 6749�6767.[2]       (a) K. V. Rajendran, D. G. Gilheany, Chem. Commun. 2012 , 48, 817-819. (b) K. V. Rajendran, D. G. Gilheany, Chem. Commun. 2012 , 48, 10040-10042.[3]       N. Kenny, K. V. Rajendran, E. V. Jennings, D. G. Gilheany, Chem. Eur. J. 2013, 42, 14210-14214[4]       K. V. Rajendran, L. Kennedy, C. T. O'Connor, E. Bergin, D. G. Gilheany, Tetrahedron Lett. 54,2013 ,7009-7012.[5]       K. V. Rajendran, L. Kennedy, D. G. Gilheany, Eur. J. Org. Chem. 2010, 5642 � 5649.

Stereomutation of scalemic phosphine oxides by chlorophosphonium salts

248th National Meeting (2014)

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