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Keywords:

  • catalytic aza-Wittig reaction;
  • phosphine redox cycle;
  • 4(3H)-quinazolinones;
  • tetramethyldisiloxane;
  • vasicinone

Abstract

Thumbnail image of graphical abstract

The catalytic aza-Wittig reaction based on a phosphine/phosphine oxide catalytic cycle is reported. The by-product triphenylphosphine oxide (Ph3PO) was reduced in situ to triphenylphosphine (Ph3P) with good chemselectivity so that the aza-Wittig reaction can be accomplished by using merely a catalytic amount of triphenylphosphine. The reaction has been demonstrated in an efficient synthesis of 4(3H)-quinazolinones and the natural product (S)-vasicinone in high yields, by using a catalytic amount of triphenylphosphine (5%) and the tetramethyldisiloxane/titanium tetraisopropoxide [TMDS/Ti(O-i-Pr)4] reductant system (81–95% yields and >99% ee).