Magnesium oxide as a heterogeneous and recyclable base for the N-methylation of indole and O-methylation of phenol using dimethyl carbonate as a green methylating agent

Abstract

N-methylation of indole and O-methylation of phenol have been developed using MgO as a heterogeneous, inexpensive, easily available, recyclable solid base and dimethyl carbonate as a green methylating reagent.

Palladium(II)‐Catalyzed C3‐Selective Friedel–Crafts Reaction of Indoles with Aziridines

“…1 H NMR (500 MHz, CDCl 3 ): δ =7.60 (d, J =7.5 Hz, 1 H), 7.25 (d, J =8.0 Hz, 1 H), 7.19 (t, J =7.0 Hz, 1 H), 7.08 (t, J =7.0 Hz, 1 H), 6.94 (d, J =3.0 Hz, 1 H), 6.45 (d, J =3.0 Hz, 1 H), 3.64 ppm (s, 1 H). These data matched the literature data …”

Efficient total synthesis of neocryptolepine and synthetic access to 6-methylquinindoline from a common intermediate

“…Next, the nal N-methylation stage was approached, with the use of a MgO-catalyzed methylation with dimethyl carbonate (DMC). 26 The latter is a versatile and safe replacement of more hazardous alkylating agents, such as MeI, Me 2 SO 4 and MeOTf, which have been widely used in the eld of indoloquinoline chemistry; further, it does not produce harmful reaction waste.…”

Recent Advances in Methylation: A Guide for Selecting Methylation Reagents

“…Among several solid oxide bases (MgO, ZnO, ZrO 2 , CeO 2 , CaO, and Al 2 O 3 ), MgO was selected by the Bhanage group for the methylation of indoles and phenols under microwave conditions (170 °C, 30 min). The protocol works well for the N‐methylation of imidazole, but no products are formed on the aliphatic N‐containing heterocycles …”

“…The protocol works well for the Nmethylation of imidazole, but no products are formed on the aliphatic N-containingh eterocycles. [144] In 2009, Laurila et al demonstrated an N-methylationo f electron-deficient pyrroles by using DMC both as reagent and solvent, plus catalytic 1,4-diazabicyclo[2.2.2]octane (DABCO), and DMFa sc o-solvent. It is noteworthy that the method works well even at 90 8Ca nd gives, in general, high to excellent yields (Scheme 22).…”