Asymmetric Ring-Opening Reactions of Unsaturated Heterocycles

7 Asymmetric Ring-Opening Reactions of Unsaturated Heterocycles 

Ring-opening reactions of unsaturated heterocycles represent a promising alternative to the allylation reactions described in previous sections. In many instances the products that can be isolated from such transformations are not otherwise readily accessible [38, 40, 41]. These transformations share mechanistic similarities with carbometalation of olefins (Section 13.6). Because the products are formally derived from allylic displacement reactions, however, they are included in the current chapter. 

H Chemistry contributes broadly to the foundations of technology, and thus it is particularly difficult to guess its future impact a new chemical reaction might be used to make a cancer therapeutic or a chemical weapon. (Whitesides, 2004) [6]  

3 Negishi, E.-i. (2002) Handbook of Organopalladium Chemistry for Organic Synthesis (eds E.-i. Negishi and A. de Meijere), Vol. 1, Wiley-lnterscience, pp. 3—15. 

4 Pfaltz, A. and Lautens, M. (1999) Comprehensive Asymmetric Catalysis l-lll (eds E.N. Jacobsen, A. Pfaltz and H. Yamamoto), Vbl. 2, Springer-Verlag, Berlin, pp. 833-884. 

---

Palladium remains the most widely recognized transition metal to effect stereoselective allylic alkylation reactions. Consequently, diastereoselective and enantioselective Pd-catalyzed processes are extensively discussed in Sections 14.2 and 14.3. More recent advances in the field of metal-catalyzed al-lylation reactions include the use of chiral iridium complexes, dealt with in Section 14.4 [33, 34]. Section 14.5 describes selected stereoselective copper-catalyzed SN2 -allylation reactions [33, 35-37], while a brief presentation of allylation reactions with other transition metals including Mo and Rh is given in Section 14.6 [8, 13, 33, 38, 39]. The closing Section 14.7 deals with selected methods for asymmetric ring-opening reactions of unsaturated heterocycles [38, 40, 41]. 

---