Observation of intermediates in reaction of non-stabilized phosphonium ylide containing phosphaboratatriptycene skeleton with PhCHO

Abstract

The signals of intermediates in the reaction of non-stabilized phosphonium ylide containing a phosphaboratatriptycene skeleton with PhCHO were observed as broad singlets at around −4.56 ∼ −5.77 ppm between −50 °C and −10 °C by variable temperature (VT) ³¹P{¹H} NMR spectroscopy. The signals assignable to the same intermediates were also observed from −90 °C to −10 °C in the deprotonation of the diastereomeric mixture of β-hydroxyalkylphosphonium salts containing a phosphaboratatriptycene skeleton with TMS₂NNa by VT-³¹P{¹H} NMR spectroscopy. The results strongly suggested that the observed phosphorus signals were not assigned to 1,2-oxaphosphetanes but betaine intermediates because the signals due to 1,2-oxaphosphetanes containing phosphaheteratriptycene skeletons with Group 14 and 15 elements were observed around −55.7 ∼ −82.8 ppm except for Bi.

Graphical Abstract

Keywords:

• Wittig reaction
• intermediate
• 1,2-oxaphosphetane
• betaine
• VT-³¹P{¹H} NMR spectroscopy
• heteroatom effect

Acknowledgements

The authors thank to Professor Takayuki Kawashima for informative advice.

Disclosure statement

No potential conflict of interest was reported by the authors.