Transmetalation pathways, Stille coupling

Other mechanisms are possible, however. For example, the original mechanism proposed for the transmetalation step in Stille coupling (Section 12-4-2) involved an acyclic SE2 (Section 8-4-1) pathway (equation 12.54), which proceeds through transition state 39 such that R is transferred with inversion of configuration.116 We will further discuss this dichotomy in Section 12-4-2. 

Recent comprehensive studies by Espinet et al. on the Stille reaction and related transmetalation reactions revealed the mechanistic features of transmetalation of organostannanes with Pd complexes, which is a key step in the Pd-catalyzed coupling of organic halides or triflates with organostannanes [109,110]. The reaction can follow two basically different pathways involving a cyclic or an open transition state in the transmetalation step (Scheme 5.15). 

Alvarez R, Perez M, Faza ON, de Lera AR (2008) Associative transmetalation in the Stille cross-coupling reaction to form dienes Theoretical insights into the open pathway. Organometallics 27 3378-3389... 

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