Synthesis of 2-substituted 7-hydroxybenzofuran-4-carboxylates via addition of silyl enol ethers to o-benzoquinone esters.
Mukaiyama Michael addition of silyl enol ethers 13 to the 1,2-quinone-4-carboxylate 6 (formed in situ by oxidation of the catechol ester 8) afforded the 2-subsituted 7-hydroxybenzofuran-4-carboxylates 14 in fair to good yields. Alkyl and aryl systems work well, but highly electron-rich silyl enol ethers could not be used because of competing oxidation.
Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095, USA. jung@chem.ucla.edu
Michael E
ME
Jung
Felix
F
Perez
D001572:Benzofurans / Q000138:chemical synthesis* / Q000737:chemistry; D016227:Benzoquinones / Q000737:chemistry*; D002264:Carboxylic Acids / Q000138:chemical synthesis*; D002384:Catalysis; D003500:Cyclization; D004952:Esters; D004987:Ethers / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D012821:Silanes / Q000737:chemistry*
D001572:Benzofurans; D016227:Benzoquinones; D002264:Carboxylic Acids; D004952:Esters; D004987:Ethers; D012821:Silanes; C025225:2-benzoquinone