- Tandem diastereo- and enantioselective preparation of aryl and alkyl cyclopropyl carbinols with three adjacent stereocenters using perhydrobenzoxazines and diethylzinc
-
The enantio- and diastereoselective one-pot ethylation/cyclopropanation is efficiently promoted by a chiral perhydrobenzoxazine. The catalytic system tolerates a wide range of di- and trisubstituted α,β-unsaturated aldehydes and has been found to be highly diastereo- and enantioselective. Enals leading to intermediates lacking allylic strain or with either A1,2 or A1,3 strain afford the corresponding syn hydroxycyclopropanes very selectively. While α-methyl enals are successfully ethylated/ cyclopropanated, the presence of bulky substituents at the alpha position of the enal constitutes a limitation to the substrate scope. The use of 1,1-diiodoethane allows the obtention of the corresponding enantioenriched cyclopropylcarbinol, which bears carbon-substituents at all three positions of the ring, with good enantiocontrol, although moderate diastereoselectivity. A procedure for the asymmetric one-pot arylation/cyclopropanation of enals is proposed, which involves the use of triarylboroxin, diethylzinc and diiodomethane.
- Infante, Rebeca,Nieto, Javier,Andres, Celia
-
-
Read Online
- THE-PALLADIUM-CATALYSED REDUCTIVE ADDITION OF ARYL IODIDES TO PROPARGYL ALCOHOLS: A ROUTE TO γ,γ-DIARYL ALLYLIC ALCOHOLS
-
The reaction of aryl iodides with ethynyl and arylethynyl, dialkyl carbinols in the presence of the tri- or dialkylammonium formate-palladium reagent provides a convenient route to γ,γ-diarylallylic alcohols.In the presence of arylethynyl, alkylcarbinols a lack of regioselectivity was observed and mixtures of β,γ-, γ,γ-diarylallylic alcohols, and α,β-unsaturated ketones were obtained.
- Arcadi, A.,Cacchi, S.,Marinelli, F.
-
p. 5121 - 5132
(2007/10/02)
-