Ammonium Salt-Catalyzed Highly Practical Ortho-Selective Monohalogenation and Phenylselenation of Phenols: Scope and Applications

Abstract

An ortho-selective ammonium chloride salt-catalyzed direct C−H monohalogenation of phenols and 1,1′-bi-2naphthol (BINOL) with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as the chlorinating agent has been developed. The catalyst loading was low (down to 0.01 mol %) and the reaction conditions were very mild. A wide range of substrates including BINOLs were compatible with this catalytic protocol. Chlorinated BINOLs are useful synthons for the synthesis of a wide range of unsymmetrical 3-aryl BINOLs that are not easily accessible. In addition, the same catalytic system can facilitate the orthoselective selenylation of phenols.

Base‐Promoted Direct Chalcogenylation of 2‐Naphthols

“…On the basis of the above observations and previous related reports, a plausible reaction mechanism is proposed here (Scheme ). Initially, the hydrogen abstraction by the base from the hydroxyl group in 2‐naphthols generates the 2‐naphtholates anions in equilibrium.…”

Late‐Stage Direct o‐Alkenylation of Phenols by PdII‐Catalyzed C−H Functionalization

“…Besides, the reagents should be pre‐halided, through which high site‐selective of phenols is difficult to be achieved . Moreover, due to the strong electron‐donating and directing effects of the hydroxyl group, the functionalization of phenols usually leads to ortho ‐ and para ‐substituted products . Thus, the development of new approach to obtain ortho ‐vinylated phenols with good atom economy and high regioselectivity is highly essential.…”

Steric Hindrance Effect Leading to Regioselective Bromination of Phenols with HBr

“…1 H NMR (600 MHz, CDCl 3 ) δ: 7. 20 (dd,J＝9.6,2.4 Hz,1H), 7.15～7.07 (m, 1H), 6.87 (t, J＝9.0 Hz, 1H), 5.96 (br s, 1H); 13 C NMR (150 MHz, CDCl 3 ) δ: 151.00 (d,J＝242.6 Hz), 142.67 (d,J＝13.6 Hz), 128.05 (d,J＝3.7 Hz), 119.22 (d,J＝21.4 Hz), 118.74 (s), 111.96 (d,J＝8.3 Hz); MS (EI) m /z: 192, 190, 172, 163, 161, 144, 142, 111, 95, 83, 63. 4-Bromo-2-chlorophenol (3e): [18] Colorless oil. 1 H NMR (600 MHz, CDCl 3 ) δ: 7.59 (d,J＝2.4 Hz,1H), 7.32 (dd, J＝8.4, 2.4 Hz 1H), 6.90 (d,J＝8.4 Hz,1H), 5.51 (br s,…”