Synthesis of Optically Active syn Aldols Using Chiral Auxiliaries

2 Synthesis of Optically Active syn Aldols Using Chiral Auxiliaries 

Asymmetric aldol reactions utilizing chiral auxiliaries or templates have emerged as one of the most reliable methods in organic synthesis. Both syn-and anti-selective aldol reactions have been developed over the years. The field of asymmetric syn aldol reactions has been largely advanced by Evans since his development of dibutylboron enolate aldol chemistry based on amino acid-derived chiral oxazolidinones. This method requires expensive dibutylboron trifiate, hosvever, and the amino acid-derived chiral auxiliary is only readily available in one enantiomer and thus only provides one enantiomer of the syn aldol. Several methods developed on the basis of titanium enolates provide convenient access to both Evans and non-Evans syn aldol products. 

---