ChemInform Abstract: Metalation in Connection with Cross‐Coupling Reactions. Coupling of Hindered Aryls for the Synthesis of 4‐Phenylpyridines as Part of Streptonigrin and Lavendamycin Analogues.

Abstract

In view of the interest in synthetic strategies for the title alkaloids, a heterobiaryl cross-coupling between a hindered 4-iodopyridine and an arylboronic acid is required. The influence of steric and electronic factors on the course of this coupling reaction is studied. The results reveal that good yields are obtained when reaction is carried out with C-5 unsubstituted pyridine derivatives and either ortho-substituted or unsubstituted arylboronic acids ( products such as (III)). Good yields are obtained when the unsubstituted (Ib) reacts with the C-5 substituted pyridine (IV). A marked drop in the yields is observed when pyridine bears two large substituents ortho to iodine and in the phenyl ring a sterically hindering group is ortho to B(OH)2 (products such as (VII)). Bromo derivatives such as (VIII) also yield the corresponding 4-phenylpyridines. -(GODARD, A.; ROCCA, P.; POMEL, V.; THOMAS-DIT-DUMONT, L.; ROVERA, J. C.; THABURET, J. F.; MARSAIS, F.; QUEGUINER, G.; J.

Isolation, Biological Activities and Synthesis of Indoloquinoline Alkaloids: Cryptolepine, Isocryptolepine and Neocryptolepine

“…Pd-catalyzed cross-coupling reaction between boronic acid 12 and 3-fluoro-2-iodoquinoline 24 using Suzuki procedure [48][49][50][51] afforded the biaryl compound 25 which, underwent cyclization on treatment with boiling pyridinium hydrochloride [52] to give quin-doline 4 in 83% yield. The intramolecular nucleophilic displacement of fluorine with amino group is facilitated by the formation of quinoline hydrochloride.…”