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Stereoselective Oxa‐Michael Addition of Tyrosine to Propargyl Aldehyde/Esters: Formation of Benzofurans and Flavones
Author(s) -
Vasconcelos Stanley N. S.,
Oliveira Isadora Maria,
Shamim Anwar,
ZukermanSchpector Julio,
Pimenta Daniel C.,
Stefani Hélio A.
Publication year - 2019
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201900564
Subject(s) - chemistry , michael reaction , intramolecular force , propargyl , propargyl alcohol , aldehyde , moiety , stereoselectivity , organic chemistry , aryl , flavones , stereochemistry , medicinal chemistry , catalysis , alkyl , chromatography
Abstract The steroselective oxa‐Michael addition of the phenol moiety present in tyrosine and 3‐iodotyrosine to different propargyl aldehydes delivered products with predominantly Z stereochemistry, as evidenced by X‐ray crystallography analysis. When ethyl propiolate was used as the propargyl ester source, the products were achieved with exclusively E stereochemistry with yields ranging from 17% to 91%. The oxa‐Michael addition compounds served as substrates in the synthesis of 5‐ and 6‐membered heterocyclic compounds. The atmosphere applied to the reaction medium directly influenced the formation of the products. When an inert atmosphere of nitrogen was applied, a 2‐aryl‐3‐formyl‐5‐alanylbenzofuran core was selectively obtained via a Heck intramolecular reaction, while the reactions carried out under a carbon monoxide atmosphere led exclusively to 6‐alanyl‐2‐arylflavone derivatives via reductive intramolecular acylation.