General synthetic route to benz[g]isoquinolines (2‐azaanthracenes)

Abstract

Benzylic zinc reagents add with high regioselectivity to 1‐(phenoxycarbonyl) salts derived from pyridine‐3‐carboxaldehyde (1a) or 3‐acetylpyridine (1b) to yield 1‐(phenoxylcarbonyl)‐4‐benzyl‐1,4‐dihydropyridine‐3‐carboxaldehydes 5a, 5c or ketones 5b, 5d. Aromatizations of these dihydro analogues with sulfur led to the corresponding aldehydes 6a, 6c or ketones 6b, 6d. An alternate synthesis to the aldehydic precursors involved additions of benzylic zinc reagents to 1‐(phenoxycarbonyl) salts formed from methyl nicotinates which led to the corresponding methyl 1‐(phenoxycarbonyl)‐4‐benzyl‐1,4‐dihydronicotinates 7a, 7b. Aromatizations of 7a, 7b led to the corresponding pyridine esters 8a, 8b which on reduction with lithium aluminum hydride yielded the corresponding carbinols 9a, 9b. Oxidation of 9a, 9b by manganese dioxide afforded aldehydes 6e, 6f. Aldehydes 6a‐f were readily converted into the benz[g]isoquinolines 10a‐f on heating in polyphosphoric acid.

Anthracene-Based Zwitterion with a Small HOMO–LUMO Energy Gap

“…Compound 4b was synthesized in seven steps from 3-benzoylpyridine (6) according to the literature for synthesizing 2-azaanthracene derivatives (Scheme 1). 14 S2 and S3). 1 H NMR signals of 4b shifted upfield compared to those of 5b•BF 4 − (Figure 3b).…”

“…Compound 4b was synthesized in seven steps from 3-benzoylpyridine (6) according to the literature for synthesizing 2-azaanthracene derivatives (Scheme 1). 14 Thus, the 3-(tert-butyl)-4methoxybenzyl group was introduced by the reaction of 3- This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.…”

“…4b was synthesized in 7 steps from 3-benzoylpyridine (6) according to the literature for synthesizing 2-azaanthracene derivatives (Scheme 1). 14 Thus, 3-(tert-butyl)-4-methoxybenzyl group was introduced by the reaction of 3-benzoyl-1-(phenoxycarbonyl)pyridinium derived from 6 with the corresponding organozinc reagent 15 to give 7, which was reacted with sulfur to give 8. Acid-promoted intramolecular cyclization followed by dehydration gave 2azaanthracene derivative 9.…”

Fluorescence Studies of Amine-substituted Azaanthracene Metal Complexes

“…The already appropriated reaction by Krapcho and Gilmor [64] during the master thesis will be used here in a modified way. Scheme 2.1 shows the first steps of the reaction pathway to 5,10-dimethyl-2-azaanthracene (3).…”

“…Scheme 2.1: First part of the synthesis of 5,10-dimethyl-2-azaanthracene, showing the reaction to 1-phenoxycarbonyl-3-acetyl-4-phenylethyl-1,4-dihydropyridine (1). [64] The modified starting materials provide the desired methyl groups highlighted in blue. In the upper part of the reaction, the protecting group phenyl formate is introduced to the nitrogen atom of the pyridine derivative.…”