Abstract
The allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions is described. The synergistic palladium/copper-catalyzed reaction of aromatic aldehydes, allylic carbonates, and a silylboronate produces the corresponding homoallylic alcohol derivatives. This process involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species and the subsequent palladium-catalyzed allylic substitution.
Highlights
Introduction αAlkoxy-substituted carbanions (α-alkoxyalkyl anions) are useful C(sp3) nucleophiles for the construction of alcohol units found in a majority of pharmaceuticals, agrochemicals and bioactive natural products
The allylic cross-coupling reaction did not occur at all without Pd(OCOCF3)2–DPPF or (SIPr)CuCl, and the palladium and copper catalysts cooperatively acted in the allylic cross-coupling
Scheme 3 shows the substrate range of aromatic aldehydes 1 and allylic carbonates 2
Summary
Introduction αAlkoxy-substituted carbanions (α-alkoxyalkyl anions) are useful C(sp3) nucleophiles for the construction of alcohol units found in a majority of pharmaceuticals, agrochemicals and bioactive natural products. A nucleophilic α-silyloxybenzylcopper(I) species can be generated catalytically from aromatic aldehydes through the 1,2-addition of a silylcopper(I) species followed by [1,2]-Brook rearrangement and successfully trapped with aryl bromides under palladium catalysis (Scheme 1). The allylic cross-coupling of aromatic aldehydes and allylic carbonates with a silylboronate by the merging of a copper–N-heterocyclic carbene catalyst and a palladium–bisphosphine catalyst produced homoallylic alcohol derivatives [12,13,14].
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