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J Org Chem. 2003 Nov 28;68(24):9513-6.

Synthesis of 2,3-substituted thienylboronic acids and esters.

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  • 1Novo Nordisk A/S, Novo AllĂ©, DK-2880 Bagsvaerd, Denmark. clcp@novonordisk.com

Abstract

A noncryogenic protocol for the synthesis of 2-substituted 3-thienylboronic acids and esters as well as 3-substituted 2-thienylboronic acids and esters has been developed. Electrophiles were introduced regiospecifically in the 2-position of 2,3-dibromothiophene and in the 3-position of 2-bromo-3-iodothiophene by halogen-magnesium exchange followed by quenching with electrophiles. Palladium-catalyzed borylation of the 2,3-substituted halothiophenes with pinacolborane and P(t-Bu)3 as ligand for Pd produced 9 and 10. The borylation protocol was tolerated by a range of functional groups; however, strongly electron-withdrawing substituents decreased the stability of the thienylboronic acids and esters.

PMID:
14629185
[PubMed]
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