18791-98-5Relevant articles and documents
Regiocontrolled Halogen Dance of Bromothiophenes and Bromofurans
Mari, Daichi,Miyagawa, Naoki,Okano, Kentaro,Mori, Atsunori
, p. 14126 - 14137 (2018/11/23)
The LDA (lithium diisopropylamide)-promoted regiocontrolled halogen dance of α-bromothiophenes and α-bromofurans is described. Bromothiophenes bearing a diethyl acetal moiety undergo selective deprotonation at the β-position adjacent to the bromo group. In contrast, oxazoline, ester, and amide groups act as directing groups in the initial lithiation step to generate a carbanion at the β-position neighboring the directing group to exclusively give the other regioisomer. These results can be applied to the regiocontrolled halogen dance of bromofuran derivatives.
Synthesis of 2,3-Substituted Thienylboronic Acids and Esters
Christophersen, Claus,Begtrup, Mikael,Ebdrup, Soren,Petersen, Henning,Vedso, Per
, p. 9513 - 9516 (2007/10/03)
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.
