Use of Suzuki cross-coupling as a route to 2-phenoxy-6-iminopyridines and chiral 2-phenoxy-6-(methanamino)pyridines

作者：Davies Christopher J; Gregory Andrew; Griffith Phillip; Perkins Tom; Singh Kuldip; Solan Gregory A^*

来源：Tetrahedron, 2008, 64(42): 9857-9864.

DOI：10.1016/j.tet.2008.08.019

• Suzuki
• cross-coupling
• 2-phenoxy-6-iminopyridines
• 2-phenoxy-6-(methanamino)pyridines
• chiral

The anisyl boronic acids, 2-OMe-3-R(2)-5-R(1)-C(6)H(2)B(OH)(2) (R(1)=R(2)=H (a); R(1)=H, R(2)=Ph (b); R(1)=Me, R(2)=H (c); R(1)=Cl, R(2)=H (d); R(1)=t-Bu, R(2)=H (e)), have been employed in Suzuki cross-coupling reactions with either 2-bromo-6-formylpyridine (1) or 2-bromo-6-acetylpyridine (11) generating, following a facile deprotection step, the 2-phenoxy-6-carbonylpyridines, 2-(2'-OH-3'-R(2)-5'-R(1)-C(6)H(2))-6-(CH=O)C(5)H(3)N (R(1)=R(2)=H (1a); R(1)=Me, R(2)=H (1c); R(1)=Cl, R(2)=H (1d); R(1)=t-Bu, R(2)=H (1e)) and 2-(2'-OH-3'-R(2)-5'-R(1)-C(6)H(2))-6-(CMe=O)C(5)H(3)N (R(1)=R(2)=H (2a); R(1)=H, R(2)=Ph (2b)). Condensation reactions of 1 and 2 with 2,6-diisopropylaniline proceed smoothly to give the 2-phenoxy-6-iminopyridines, 2-(2'-OH-3'-R(2)-5'-R(1)-C(6)H(2))-6-{CH=N(2,6-i-Pr(2)C(6)H(3))}C(5)H(3)N (R(1)=R(2)=H (3a); R(1)=Me, R(2)=H (3c); R(1)=Cl, R(2)=H (3d); R(1)=t-Bu, R(2)=H (3e)) and 2-(2'-OH-3'-R(2)-5'-R(2)-C(6)H(2))-6-{CMe=N(2,6-i-Pr(2)C(6)H(3))}C(5)H(3)N (R(1)=H, R(2)=Ph (4a), R(1)=H, R(2)=Ph (4b)). Reduction of the imino unit (and concomitant C-C bond formation) in 3 can be achieved by treatment with trimethylaluminium or methyllithium which, following hydrolysis, furnishes the racemic chiral 2-phenoxy-6-(methanamino)pyridines, 2-(2'-OH-3'-R(2)-5'-R(1)-C(6)H(2))-6-{CHMe-NH(2,6-i-Pr(2)C(6)H(3))}C(5)H(3)N {R(1)=R(2)=H (5a); R(1)=Me, R(2)=H (5c); R(1)=Cl, R(2)=H (5d); R(1)=t-Bu, R(2)=H (5e)). This work represents a straightforward and rapid synthetic route to libraries of sterically and electronically variable phenoxy-substituted imino- and methanamino-pyridines, which are expected to act as useful ligands or proligands for late and early transition metal-mediated alkene polymerisation catalysis.

• 出版日期2008-10-13