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The Stille Reaction: A Density Functional Theory Analysis of the Transmetalation and the Importance of Coordination Expansion at Tin

2003; American Chemical Society; Volume: 22; Issue: 20 Linguagem: Inglês

10.1021/om020519z

1520-6041

Elio Napolitano, Vittorio Farina, Maurizio Persico,

Asymmetric Hydrogenation and Catalysis

The transfer of an alkynyl group from Sn(C⋮CH)4 (6) to PdBr(PH3)2(C⋮CH) (7) was studied computationally. Nucleophilic assistance at the Sn atom during the transmetalation was modeled by using ammonia as the nucleophile. Eight distinct reaction modes have been found: they are of the cyclic or open type when only one phosphine is bound to Pd, and open when two phosphines are bound to Pd. The stabilization effect produced on the transition state by the nucleophilic assistance at Sn can be almost 10 kcal/mol. A number of stable π-complexes resulting from the substitution of either Br or PH3 of 7 by the alkynyl group triple bond of 6 have also been found, which may correspond to the intermediates postulated in many mechanistic studies of the Stille coupling.