5,6,7,8-Tetrahydronaphthalen-1-amine as Precursor for Thiazolidinones and Benzothiazepinones: Synthesis and Atropisomeric RelationshipCNPq (307330/2012-5).
Received: 09 June 2017
Accepted after revision: 13 July 2017
10 August 2017 (eFirst)
The one-pot reaction of 5,6,7,8-tetrahydronaphthalen-1-amine, mercaptoacetic acid, and arenealdehydes having strong and weak electron-withdrawing groups gave the corresponding 1,3-thiazolidin-4-ones (47–70%). When arenealdehydes bearing strong and weak electron-donating groups were used as precursors, the 1,4-benzothiazepin-2-ones were obtained (30–72%) by p-TsOH catalysis. All compounds are unknown and were characterized by GC-MS and NMR techniques, and available crystals by X-ray diffraction studies. The atropisomerism phenomenon was observed in several 1,3-thiazolidin-4-ones as confirmed by VTNMR method. The Tc was established as 332 K and the energy required for the interconversion of one atropisomer into another is around 16.8 kcal·mol–1. Chemical quantum calculation and NOESY displayed that more stable isomer has the tetrahydronaphthalene portion below the five-ring plane. Only a small difference between isomers (–0.21 to –0.84 kcal·mol–1) was observed by calculated energy.