Stereoselective synthesis of unsymmetrical ß,ß-diarylacrylates by a Heck-Matsuda reaction: versatile building blocks for asymmetric synthesis of ß,ß-diphenylpropanoates, 3-aryl-indole, and 4-aryl-3,4-dihydro-quinolin-2-one and formal synthesis of (-)-indatraline.
J Org Chem
; 76(3): 857-69, 2011 Feb 04.
Article
em En
| MEDLINE
| ID: mdl-21241065
ß,ß-Disubstituted α,ß-unsaturated esters may serve as valuable derivatives for the preparation of other highly functionalized systems found in many natural products and marketed drugs. The stereoselective synthesis of unsymmetrical ß,ß-diarylacrylate compounds possessing two similar aromatic groups remains a substantial challenge. A simple and convenient stereoselective protocol for the preparation of ß,ß-disubstituted acrylates via a Heck-Matsuda reaction is reported. Good to high yields were accomplished by a "ligand-free" Pd-catalyzed arylation reaction of cinnamate esters with arenediazonium tetrafluoroborates. Both electron-deficient and electron-rich arenediazonium salts could be employed as arylating reagents, and cinnamate esters were generally more reactive when substituted with an electron-donating group. The overall methodology is highly stereoselective, and this attribute was taken advantage of in the asymmetric Cu-catalyzed 1,4 reduction reaction to provide ß,ß-diarylpropanoates in high enantioselectivities. The synthesis of a 3-aryl indole and a chiral 4-aryl-2-quinolone from ß,ß-diarylacrylates was achieved by cyclization in the presence of a diphosphine ligated CuH catalyst. A convenient route for the asymmetric formal synthesis of the psychoactive compound (-)-Indatraline is also presented.
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2011
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Article