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. 2019 May 20;20(10):2489. doi: 10.3390/ijms20102489

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© 2019 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Scheme 1 — Reagents and conditions: (i) NH₂(CH₂)_nBr, Et₃N, THF, rt, 5 h, 50–70%; (ii) thiourea, THF, 70 °C, overnight, 40–60%; (iii) tetramethylthiourea, THF, 70 °C, overnight, 55%; (iv) N¹-(6-bromohexyl)-N¹-methylbenzene-1,4-diamine, Et₃N, THF, rt, 5 h, 35–37%; (v) thiourea, THF, 70 °C, overnight, 45–53%; (vi) tetramethylthiourea, THF, 70 °C, overnight, 45–55%; (vii) 9a~b, Et₃N, THF, rt, 5 h, 50–70%; (viii) HCl, DCM, 3 h, 90–95%; (ix) R₁NH₂, Et₃N, THF, rt, 5 h, 50–65%; (x) 1-(3-bromopropyl) piperidine, K₂CO₃, THF, rt, overnight, 40%.