Mechanism of Synthesis of Tröger and Spiro‐Tröger Base Derivatives Starting from Naphthyl‐ and Anthracenylamines: A Computational Study

Abstract

Tröger’s bases (TB) have enormous applicability in differentareas of science and technology. The mechanisms of reactionof different aminoaromatics with formaldehyde in acid mediaare described in depth using DFT calculations and modelsynthesis from our group. When different naphthylamines andanthracenylamine were used, a mixture of products wasobtained, highlighting the corresponding TB, acridine and anovel isomer of TB, called SpiroTB, depending on the aminoprecursor and reaction conditions. Using methyl-6-amino-naphthalene-2-carboxylate, ten possible synthesis pathways forTB, SpiroTB and acridine were explored thoroughly on theirfree energy surfaces. The most likely pathways were alsoevaluated for 2-aminonaphthalene, 2-aminoanthracene and 2-methoxy-6-amino-naphthalene. It was found that the firstformaldehyde enters on a carbon ortho to the amino and thedistribution of products is driven by the relative energies of thetransition states required to form the methylene bridgebetween two aromatic carbons and/or between an orthocarbon and the nitrogen of the second aminoaromatic. Theabsence of spiroTB starting from 4-bromoaniline was alsoexplained.