Chelation-Controlled Additions to α‑Silyloxy Aldehydes: An Autocatalytic Approach

The Felkin–Anh model has been widely accepted to describe stereochemical outcomes in nucleophilic additions to α-silyloxy carbonyl compounds. Herein, it is demonstrated that chelation-controlled additions can be performed using dialkylzinc reagents in the presence of chlorotrimethylsilane with good to excellent diastereoselectivities. Ethyl zinc chloride, the Lewis acid responsible for promoting chelation, is generated <i>in situ</i> in an autocatalytic fashion. This approach circumvents its use in stoichiometric amounts

Diastereoselective Chelation-Controlled Additions to β-Silyloxy Aldehydes

A general diastereoselective method for the addition of dialkylzincs and (<i>E</i>)-di- and (<i>E</i>)-trisubstituted vinylzinc reagents to β-silyloxy aldehydes is presented. This method employs alkyl zinc triflate and nonaflate Lewis acids and affords chelation-controlled products (6:1 to > 20:1 dr)

Alkenes as Chelating Groups in Diastereoselective Additions of Organometallics to Ketones

Alkenes have been discovered to be chelating groups to Zn­(II), enforcing highly stereoselective additions of organozincs to β,γ-unsaturated ketones. ¹H NMR studies and DFT calculations provide support for this surprising chelation mode. The results expand the range of coordinating groups for chelation-controlled carbonyl additions from heteroatom Lewis bases to simple C–C double bonds, broadening the 60 year old paradigm