Copper‐Catalysed, Enantioselective Desymmetrisation of meso Cyclic Allylic Bis(diethyl phosphates) with Organozinc Reagents

Abstract

A highly regio-, diastereo-and enantioselective desymmetrization of five-, six-, and seven-membered meso, cyclic allylic bis(diethyl phosphates) (3-5) with organozinc reagents was developed, using catalytic amounts (10 mol%) of [Cu(OTf)] 2 ·C 6 H 6 and two different classes of chiral ligands: Schiff bases 1 and phosphoramidites 2. Good to excellent enantioselectivities were obtained for every substrate by a subtle balance of ligand structure and experimental conditions. In particular, ee's of up to 88 % were obtained for the fivemembered ring substrate 3 with ligands 1cjo and 1cjm using Et 2 Zn (94 % ee with Me 2 Zn, 88 % ee with nBu 2 Zn). Schiffbase ligands 1 were not effective with the six-and seven-

The Copper-Catalyzed Asymmetric Allylic Substitution

“…Dimethylzinc gave even better selectivity (94% ee), albeit in moderate yield (40%). Even phenylation was possible, using a mixture of Ph 2 Zn and Me 2 Zn, but with lower ee (68%) [45] [46]. This is the only report on an efficient transfer of a phenyl group.…”

Transition metals in organic synthesis: Highlights for the year 2005

“…Copper catalyzed desymmetrizations of cyclic meso allylic bisphosphonates using alkylzinc reagents [632]. Copper catalyzed asymmetric alkylations of ␥-phosphate-␣,␤-unsaturated esters in the ␣-position using dialkylzinc reagents (Eq.…”

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

“…[196] Des Weiteren wurde die Desymmetrisierung von cyclischen Allylphosphaten durch Kupfer/Phosphoramidit-katalysierte allylische Alkylierung mit Dialkylzinkreagentien beschrieben (Schema 31). [197,198] …”