Computational Investigations of Enantioselection in Carbon-Carbon Bond Forming Reactions of Ruthenium Guanidinobenzimidazole Second Coordination Sphere Hydrogen Bond Donor Catalysts

摘要

The NH2 group of 2- gu a(n.cidHin) bcielinNziniMied2a za nIde (GBI) can be replaced) NFI,,A.CH)1_,pF26_4 ((sRli, c,,c)5 elaborated f _.,....,,, (-,-i4N,ie2by (ARc - salts (SRRcR)- l (11 to thet,niecni4arituioriP'a2)r4e,_chelate enR R... T.T.)R1, (CO) t ksv - These catalyzehighly antiTh se2 pF6Css and in i, R, _h i-r_, -) ti R.-. c,. _) -+-,-,,-,-6..t oa lective additions oft 1,i3s.dfoicrarebrioannytliocsoemiePcofitionnda[rt(eo spilicrorbeldkebnyes'DFTe mechanism and vas First, the parent GBI, complex ti 51-15)Ru(c0)calculiti+ Dnns--- (i+pF6-) is examined be used elcviitells ahatsria 11(nyllY(GBI)] i i- 6, chirality and must_ The dicari-JonYl ruthenium-centered 2+pF. auilne) as it lacks the internal base of6 compound initially hydrogen bonds to the NH triad of the GBI ligand, but the transition states leading to each product enantiomer are essentially equal in energy. In i y c contrast, after similar bon ding of the dcarbonl compound to (SR RcR)- or (R.RcRc)-2'PF.-, a Proton is transferred to the :NMez moiety, giving an enolateand aHNMez group. The latter mediates the introduction of trans-fi face -nitrostyrene such that one enolate irattacks the Cm=Cre.ph face to give an addition product with an R configuration., in agreement with exPerimerit" Thus, the configurations of the catalyst carbon stereocenters control the Product stereochemistrY, Interactions in competing transition states are analyzed.