Facile Total Synthesis of (±)‐Nimbiol

Abstract

A facile total synthesis of (±)-nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a, an improved oxidation system of CrO3/H2O/HOAc/NaOAc was used.

A Facile Demethylation of Ortho Substituted Aryl Methyl Ethers Promoted by AlCl3

“…The nitrobenzene derivatives (entries [13][14] were prepared by nitration of corresponding phenyl methyl ether. The 2methoxy-1-formylnaphthalene and 1-methoxy-2-formylnaphthalene (entries [17][18] were prepared through the Reimer-Tiemann reaction and then subsequent conventional methylation protocol.…”

“…1, it is quite clear that the signal at 3.02 ppm gradually increased during the reaction. The formation of chloromethane was inferred in both 1 H and 13 C NMR spectra during the reaction NMR scan (the chemical shift of CH 3 Cl is 3.02 ppm in 1 H NMR, 25.88 ppm in 13 C NMR, respectively). At the same time, the GC-MS analysis of the gas in reaction vessel illustrated the existence of chloromethane in the demethylation reactions (m/z: 50).…”

“…Melting points were measured on a Kofler apparatus and were uncorrected. The 1 H NMR and 13 C NMR data were recorded in CDCl 3 solution with Bruker AM-200 or AM-400 MHz spectrometers. The chemical shifts are reported in ppm relative to TMS or CDCl 3 .…”

“…12 In our effort to synthesise this kind of naturally occurring terpenoids [13][14][15] , compound 1a was obtained by a Jones' oxidation of the key intermediate 2a. 12 In our effort to synthesise this kind of naturally occurring terpenoids [13][14][15] , compound 1a was obtained by a Jones' oxidation of the key intermediate 2a.…”

“…Nimbosidione 1b is a natural product isolated from the stem bark of Azadirachta indica by Siddiqui. 12 In our effort to synthesise this kind of naturally occurring terpenoids [13][14][15] , compound 1a was obtained by a Jones' oxidation of the key intermediate 2a. In our original plan, we intended to synthesise 2a by a conventional acetylation reaction of compound 4 with AcCl and AlCl 3 .…”